ACES U-boat commanders of outstanding records, credited with sinking large amounts of Allied shipping.
ACOUSTIC TORPEDO A torpedo which detects the target ship by means of sound and is controlled by this sound so as to steer towards the ship and eventually hit it.
ADMIRALTY The headquarters staff of the British Navy. Also used in the same sense for German Navy as "German Admiralty."
AHEAD-THROWN (A) Weapon: an antisubmarine weapon used by surface craft which is projected ahead of the ship, usually to a distance of about 300 yd; (B) attack: an attack employing an ahead-thrown weapon.
AIMING ERRORS Errors in aircraft attack arising from inaccuracies in dropping bombs, or firing rockets, i.e., errors in aiming the weapon.
A.N.D. Admiralty Net Defense; a net suspended along the sides of a ship to catch torpedoes.
APPROACH ERROR Error in surface craft antisubmarine attack which would exist without submarine evasion. See ATTACK ERROR and EVASION ERROR.
ANTISUBMARINE ATTACK PLOTTER [ASAP] An electronic device for plotting positions of own ship and submarine during attack. Sonar echoes are plotted automatically on a large cathode-ray tube of long persistence.
ANTISUBMARINE SHIP Any naval ship used for attacking submarines, i.e., destroyers, destroyer escorts, frigates, sloops, corvettes, trawlers, patrol craft [PC], sub chasers [SC], suitably equipped minesweepers, etc.
ASDEVLANT Anti-Submarine Development Detachment, Atlantic Fleet; an organization set up to test and develop antisubmarine equipment and tactics for its use.
ASDIC British echo-ranging sound gear, equivalent to United States sonar. Name is derived from Anti-Submarine Detection Internal Committee, which pioneered the development of such equipment.
ASG (RADAR) United States Navy airborne S-band (10-cm) search radar, introduced early in 1943.
ASSESSMENT An estimate of the damage done to a U-boat resulting from an attack by an antisubmarine craft. This estimate is made by a special committee on the basis of all available evidence. Assessments range from "A" - U-boat known to be sunk, to "I" - attack not on a U-boat.
ASV Air-to-surface-vessel radar, that is, airborne radar for searching for surface ship targets.
ASWORG Anti-Submarine Warfare Operations Research Group. A group of civilian scientists attached to Tenth Fleet Headquarters. Later known as ORG when transferred to COMINCH Headquarters.
ATTACK Release of one or more weapons against a U-boat in a barrage or stick. Several attacks made in succession on the same U-boat (i.e., within a few hours of each other) are called an incident, but the term attack is sometimes used loosely as synonymous with "incident."
ATTACK ERROR Distance between mean point of explosion of weapons and center of submarine. See AIMING ERROR, EVASION ERROR, APPROACH ERROR.
ATTACK TEACHER A mechanical device for simulating the conditions of a surface craft attack on a submarine, used primarily for training personnel on shore.
AVC Automatic volume control in an electronic amplifier.
BALANCED FORCE A force capable of an equally effective offensive at all times, in particular, both day and night.
BARRAGE A number of depth charges or contact charges released as a group in a surface craft attack.
BDI Bearing deviation indicator, a modification to standard sonar gear giving more accurate bearings by use of lobe comparison.
BIBER A midget submarine with crew of one, developed by the Germans and used during 1944-45.
BLIND TIME The time from loss of con tact with the submarine (or release of weapons) until weapons reach U-boat depth.
BORKUM A German radar search receiver of crystal detector type covering the 75- to 300-cm band.
BRAWNING SHOT A torpedo shot fired into a convoy without being aimed at any particular ship.
CAMOUFLAGE (RADAR) Any device for reducing the range at which an object can be detected by radar, for example, nonreflecting coatings for reducing echoes.
CAM SHIPS Merchant ships fitted with catapults for launching aircraft.
CATALINA [A/C] Twin-engined seaplane (or amphibian) built by Consolidated Aircraft. Long range, but slow, with moderate bomb load.
CLASS A ATTACK An aircraft attack on a submarine in which bombs are dropped not more than 15 sec after the submarine submerges.
COASTAL COMMAND The branch of the British Royal Air Force responsible for ocean patrol and attacks on naval targets.
COMMANDED VOLUME The locus of points about au exploding charge or bomb (or about its trajectory) that have the property that a submarine with center at any of the points will be sunk.
COMMODORE (of CONVOY) A senior naval officer (or occasionally merchant captain) responsible for the navigation, signalling, and other such activities of the convoy. The escort commander, on the other hand, is responsible for its defense against the enemy and has ultimate authority.
CONTACT An instance of detection of an enemy unit. For example, when a U-boat sights a convoy it is a contact on a convoy, as when an aircraft receives a radar blip from a submarine, it is a contact on a submarine.
CONTACT FUZE A device in a bomb, rocket, or other projectile for causing it to explode on hitting the target.


CONVOY A group of merchant ships sailing together, usually defended by naval ships acting as escorts.
COORDINATED ATTACK OR INCIDENT An attack or incident in which two or more ships and aircraft (or both ships and aircraft) take part. See ATTACK and INCIDENT. Those involving both ships and aircraft are sometimes termed joint attacks (or incidents).
CORVETTE A small antisubmarine ship, usually capable only of rather slow speed.
COTCLANT Commander Operational Training Command, Atlantic Fleet, in charge of training for the Atlantic Fleet.
COUNTERATTACK An attack on a submarine which has attacked friendly ships or is threatening to do so.
COUNTERMEASURE Any action or device designed to reduce the effectiveness of sonic enemy action or device. Tactical countermeasures involve changes in tactics or operational procedures. Material countermeasures involve new equipment. These terms are used most frequently with respect to radar and homing torpedoes.
CNO Chief of Naval Operations-the naval officer (and subordinate stall) in charge of the U.S. Navy Department.
CREEPING ATTACK A coordinate attack by surface craft aimed at surprising the submarine. An "assisting ship" maintains sonar contact and directs the "attacking ship," which proceeds at slow quiet speed over the submarine without echo ranging and drops charges.
CUBA IA Antenna used with the German Tunis search receiver for S-band reception, made up of dipole and parabolic reflector.
CURLY A torpedo which follows a zigzag course.
db Decibel. A unit of sound intensity. See any textbook of general physics or acoustics.
D-DAY Day of invasion of Normandy - June 6, 1914.
DENSITY Number of objects per unit area. For example, U-boat density might be expressed as the number of U-boats per million square miles of ocean.
DEPTH FUZE A device for detonating a bomb or other weapon at a preset depth.
DESTROYER ESCORT [DE] A large antisubmarine ship (about 1,800 tons) of fairly high speed, about 18-24 knots.
DF Radio direction finding by intercepting enemy radio transmissions and obtaining their bearings with directional receivers, thereby estimating the enemy position. See HFDF.
DIRECT HIT (by torpedo) A direct hit is made by an acoustic torpedo on a ship using a noisemaker if the torpedo, while steering toward the noisemaker, hits the ship.
DISPERSION (of bombs) The variation that would exist in the explosion points of a large number of bombs of a given type if they were all dropped tinder the same conditions (in so far as conditions could be controlled).
DIVERTER A device for causing a towed noisemaker to tow at one side of the ship's wake rather than directly astern.
ELECTRASONNE German code name for a system of radio beacons used as navigational aids.
ESCORT A naval ship or aircraft used to protect a merchant ship or group of ships. Antisubmarine ships are sometimes termed escorts even when engaged in offensive operations.
ESCORT CARRIER [CVE] A small aircraft carrier usually built on a merchant vessel bull and designed to fly antisubmarine planes. Escort carriers were actually used mostly in offensive operations, only infrequently on escort duties.
ESCORT COMMANDER Naval officer in command of forces assigned for defense of convoys.
ESCORT GROUP A group of antisubmarine ships which are operated as a unit.
EVASION ERROR Error in antisubmarine attacks introduced by evasive maneuvers on the part of the submarine.
EVASIVE ROUTING Routing to avoid known submarine positions.
EXCHANGE RATE Ratio of merchant vessels sunk by submarines to submarines sunk by antisubmarine vessels.
FAT German designation for a torpedo which runs a zigzag course, with nature of u zigzag not adjustable. See LUT.
FERRET An aircraft equipped with receivers for monitoring enemy radar transmissions.
FLEET AIR ARM British carrier and ship-based aircraft.
FLEET AIR WING 7 This air wing was based in Britain until the end of World War II.
FLIEGE German code name for S-band antenna of Tunis GSR. See CUBA IA.
FLIP-FLOP CONTROL Rudder control for a homing weapon which can be only in central position or hard over port or starboard.
FLYING FORTRESS A four-engine Boeing bomber used to a small extent for antisubmarine patrol.
FOLLOW-UP (of contacts) Effort to gain contact with a submarine whose position was accurately known at an earlier time by virtue of a previous contact.
FOURTH FLEET United States naval forces which were based in the South Atlantic; a subdivision of the Atlantic Fleet.
FOXER British towed noisemaker gear for decoying German acoustic torpedoes, consisting of two parallel bar noisemakers and diverters. Near the end of the war UNI-FOXER, a single noisemaker, was employed. See FXR.
FRIGATE A large British antisubmarine ship (about 2,000 tons) of long endurance but moderate speed, 15-18 knots.
FXR United States single towed noisemaker of parallel bar type (See FOXER).
GAMBIT An aircraft search for follow-up of contacts in which the aircraft leaves the most probable initial submarine position and flies at some distance from it for some time, in the hope that the submarine will return to the surface where it can be sighted when the aircraft returns to the area.
GAP, MID-OCEAN The mid-ocean area which could not be patrolled by land-based aircraft.
GLIDER BOMB German radio-controlled glider bomb which is guided to target by parent aircraft.


GNAT German Navy acoustic torpedo which homes automatically on noise from target ship.
GROSS TON A measure of ship size based on volume. The tonnage is the entire internal cubic capacity of the ship expressed in tons of 100 cubic feet to the ton, except certain spaces which are exempted, such as peak and other tanks for water ballast, open forecastle bridge and poop, anchor gear, steering gear, wheel house, galley, and cabins for passengers.
GSR German search receiver. i.e., German radar receiver for detecting transmissions by Allied search radar.
GU Designation for convoys from Mediterranean and Gibraltar to the United States. GUS for slow convoys, GUF for fast.
GUIDED MISSILES A missile whose course can be adjusted after launching (or firing) so as to hit the target. The adjustment may - be made b) an operator in the launching craft or ma} be automatic. Acoustic torpedoes are examples of the latter type.
HALIFAX A British four-motored heavy bomber built by Handley-Page.
HEDGEHOG An ahead-thrown weapon with mortar projected barrage of 24 contact charges, trainable to about 20 degrees off the bow of the ship.
HFDF High-frequency DF (see DF). Frequencies of about 10 megacycles are involved.
HG Designation for convoys from Gibraltar to the United Kingdom.
HOLD-DOWN HUNT A search of sufficient intensity to insure the submarine's being sighted if it surfaces.
HOMING Guiding to a source of signals. A U-boat in contact with a convoy unit's signals, thereby homing other U-boats to the scene. An acoustic torpedo steers towards the sound from a Ship's propellers, thereby homing on the target.
H2S High resolution radar of S-hand frequency for use in blind bombing.
HUDSON Twin-engine Lockheed bomber.
HUNTER-KILLER OPERATIONS Offensive operations aimed at finding and destroying U-boats, usually involving groups of surface craft and sometimes coordinated with aircraft.
HX Designation for convoys from Halifax or New York to Britain.
H2X High resolution radar of X-band frequency for use in blind bombing.
HYDROPHONE A receiver of underwater sound.
INDIRECT HIT A hit made by an acoustic torpedo which is attracted to the target ship out of a trajectory leading to a noisemaker.
INFLUENCE (fuze or pistol) A fuze activated by the change in earth's magnetic field due to the submarine's presence, which is designed to detonate the charge whenever it is close enough to the submarine to be effective.
INTERCEPT RECEIVER Radar search receiver (see GSR).
JAUMANN ABSORBER A nonreflecting covering which is effective against S- and X-band radars, made up of spaced layers of semiconducting paper. See WESCH ABSORBER.
LATERAL RANGE CURVE A curve which gives the probability of detection of an object by a searcher (who is proceeding on a straight course) as a function of distance of direct approach.
LEIGH LIGHT British aircraft searchlight used for night attacks.
LETHAL AREA The area on the ocean surface centered above an exploding depth bomb which has the following property: In a Class A attack any submarine whose center lies below the lethal area may be considered sunk, and no others.
LETHAL RADIUS The lethal radius of a given explosive charge is the maximum distance front the pressure hull at which it may be expected to do lethal damage.
LIBERATOR Four-motored heavy bomber built by Consolidated Aircraft frequently modified for use in antisubmarine patrol because of its long range and large bomb load.
LIFE (LIFETIME) OF A U-BOAT At any time the average life of a U-boat is the number of U-boats at sea divided by the rate at which U-boats are sunk per month.
LIMITING APPROACH LINES The boundary of the region from which a submarine can approach a ship or formation, drawn relative to the ship or formation.
LINE ERROR The component perpendicular to the course of attacking aircraft of the distance between center of stick and center of submarine.
LOCALIZATION Determination of exact submarine position by sonar.
LOST CONTACT (RANGE) Range at which sonar contact with submarine is lost because submarine is below sonar beam.
LUT German designation for a torpedo which runs a preset zigzag course. See FAT.
MAD Magnetic anomaly detector (or magnetic airborne detector), an aircraft instrument for detecting distortion of the earth's magnetic field due to the presence of a submarine.
MAXIMUM SUBMERGENCE Submarine tactics which involve remaining submerged as much as possible. Normally about 2 to 4 hours a day must be spent surfaced or at Schnorkel depth.
MEAN RADIAL ERROR Average distance from center of target to center of barrage.
METOX Early GSR for long wavelength radar, introduced in 1942.
MK II RADAR British long wavelength search radar used on aircraft.
MK III RADAR British airborne S-band search radar.
MK 8 DEPTH CHARGE United States influence-fuzed depth charge.
MOSQUITO British twin-engined fighter-bomber built by DeHaviland.
MOUSETRAP United States ahead-thrown weapon with rocket projected barrage of 8 or 16 contact charges. Used in small ships.


MPI Mean point of impact of a group of bombs.
MUCKE Horn antenna for X-band reception with Tunis GSR. MV. Merchant vessel.
NAXOS (1) Early non-directional GSR effective in S-band; (2) Amplifier used in Tunis GSR.
NM Noisemaker.
NOISEMAKER An artificial source of underwater noise used to conceal the noise made by a ship or submarine or to interfere with the operation of, or to decoy, acoustic devices such as acoustic torpedoes.
NORTH RUSSIAN CONVOYS Convoys from Britain around the north of Norway to Murmansk, Archangel, or other North Russian ports, and returning convoys.
OB Designation used in early years of war for convoys outward bound from Britain for America and Africa.
OBSERVANT A search plan used by surface craft, consisting of going to point of last contact with submarine and then steaming around a square centered at that point with 2-mile sides.
OG Designation for convoys from Britain to Gibraltar.
ON Designation for convoys from Britain to America. During latter part of World War II ON was reserved for 9-knot convoys, ONS being used for 7-knot.
ORG Operations Research Group. See ASWORG.
ORS Operations Research Section, title of British operations research organizations. Most frequently used in ORS/CC Operations Research Section, Coastal Command.
OS Convoy designation for convoys from Britain southbound to Sierra Leone.
PATROL CRAFT Small antisubmarine craft, normally not over about 200 feet in length.
PQ Designation for convoys from Britain to Archangel. (See NORTH RUSSIAN CONVOYS.)
PRACTICE ATTACKS Simulated attacks carried out either on the attack teacher or in exercises with a friendly ("tame") submarine.
PROXIMITY FUZE A fuze designed to detonate a bomb, charge, or projectile, when within a certain distance of the target. (See INFLUENCE FUZE.)
P/W Prisoner of war.
Q ATTACHMENT British auxiliary sound gear with beam directed below the main Asdic beam for maintaining contact with deep U-boats at short ranges.
R600 Same as METOX.
RANGE ERRORS The component parallel to the source of attacking aircraft of the distance between center of stick and center of submarine.
RDF - Type 286, Type 271 British surface craft search radar. Type 286 had fixed aerials and operated on long wavelength. Type 271 was S-band gear with rotating beam and PPI presentation.
RETRO-BOMBS Contact bombs used by aircraft in conjunction with MAD. Bombs are propelled backwards by rocket motors so as to drop vertically from aircraft.
REVERBERATION The totality of small false echoes received on sonar from objects in the ocean, its surface, and the bottom.
ROCKET Used alone the word implies forward-firing rockets of about 3-in. diameter used by aircraft. (See MOUSETRAP, for comparison.)
RUNDDIPOL Submersible GSR aerial used for long wavelength radar reception.
S-BAND Radar operating band for wavelengths of about 10 cm.
SBT Submarine bubble target. A German decoy used to produce false echoes from a cloud of bubbles.
SC Designation for 7-knot convoys from America to Britain.
SCHNORKEL U-boat combination air intake and Diesel exhaust, permitting operation on Diesels when at periscope depth. Introduced in 1944.
SCR-517 United States Army S-band airborne search radar.
SCR-717 Improved version of SCR-517.
SD RADAR United States Navy X-band airborne search radar.
SEA RETURN The totality of false radar echoes from ocean surface.
SEARCH RECEIVER A radar receiver for intercepting signals from enemy search radar and thereby being warned of his approach.
SENSITIVITY PATTERN The sensitivity of an acoustic torpedo is a diagram showing the range and bearing at which a given sound source will produce a given signal at the torpedo control mechanism.
SG United States Navy surface craft S-band search radar (see RDF, Type 271).
SHADOWING A U-boat shadowing a convoy kept in contact with it and reported information about it without attacking.
SINKING RATE The effectiveness of a U-boat in sinking ships. The sinking rate is equal to the U-boat's sweep rate times the fraction of ships contacted that are sunk.
SL (1) Convoy designation for convoys from Sierra Leone to Britain; (2) radar designation for United States Navy radar similar to SG but lighter in weight.
SLOOP Large antisubmarine ship of moderate speed, similar to frigate.
SONAR The United States Navy term for underwater sound equipment and its use. British use "Asdic" in similar way.
SONOBUOY, EXPENDABLE RADIO A small buoy capable of transmitting sounds heard in the ocean to an observer by radio. Used primarily by aircraft.
SORTIE An aircraft flight.
SQUID An ahead-thrown depth charge and associated depth determining sound gear by means of which the submarine's actual depth is automatically set into the depth charge fuze.


STEP-ASIDE A radical zigzag designed to permit a ship to approach a U-boat with minimum danger from acoustic torpedoes.
STERN CHASE An attack or pursuit course which overtakes the target from its stern.
STICK A number of bombs or depth charges dropped in a row.
STRAGGLER A ship which left a convoy because unable to maintain proper speed.
SUBMERGED APPROACH ZONE The area around a convoy from which a submarine can make a submerged approach to it.
SUNDERLAND British four-motored seaplane.
SUPPLY U-BOAT A U-boat fitted to refuel and supply other U-boats without attacking any ships itself.
SUPPORT GROUP (i.e., 2nd Support Group) A number of antisubmarine ships kept together permanently as a group to hunt U-boats and provide extra defense to convoys threatened by attack.
SWEEP RATE The number of contacts made per hour per unit of target density by a searching craft. It is expressed in square miles per hour and is the measure of searching craft's effectiveness of covering area.
SWEEP WIDTH Sweep rate divided by speed (approximately).
T-5 German acoustic torpedo (earliest models were designated T-4).
TENTH FLEET United States Navy Headquarters assigned tasks of conducting war on submarines and protecting merchant shipping.
TORPEDO DANGER ZONE Area around a ship or convoy from which a submarine has a good chance of hitting with a salvo of torpedoes.
TORPEX Recently developed explosive superior to TNT in destructive power.
TOSS BOMBING (or ROCKETING) A method of glide-bombing (or rocket-firing) in which weapons are released as the plane pulls out of the glide.
TRACKING Maintaining contact with an enemy unit so as to determine its course and speed.
TRACTRIX The curve of pursuit followed by always proceeding towards an object which is itself moving with constant course and speed.
TRANSIT, TRANSIT AREA Passage of a submarine from base to its operating area is termed a transit and the area between base and the operating area is the transit area.
TUNIS Directional GSR for interception of S-band and X-band radar. (See NAXOS, MUCKE, and FLIEGE.)
TYPE XVII-B U-BOAT Small experimental U-boats with oil-H2O2 turbine drive for submerged operations having speeds up to 24 knots.
TYPE XXI U-BOAT New type U-boat with powerful electric motors, and extra batteries permitting high submerged speed operation (up to 15 knots).
TYPE XXIII U-BOAT Similar to Type XXI, but smaller, for coastal operations.
TYPE XXVI U-BOAT Proposed ocean-going U-boat with turbine drive as in Type XVII.
TYPE 147B ASDIC British sound gear used for determining submarine depth during an attack.
TYPE 271 RADAR British shipborne 10-cm search radar. U-BOAT. Any enemy submarine of 200 tons or larger.
UG Designation for convoys from United States to Gibraltar and Mediterranean; UGS for slow convoys, UGF for fast.
U-KREUZER Large long-range U-boat.
V-1 German "buzz-bomb" or jet-propelled pilotless aircraft of moderate range.
VLR AIRCRAFT Very long-range aircraft.
VIXEN An attenuator for use with airborne radar to reduce the output as range to the target is closed, thereby confusing the GSR operator.
WANZ G-1 Long wavelength GSR, an improvement on Metox.
WEAPON LETHALITY The effectiveness of a weapon in producing damage, without regard to the accuracy with which it can be placed.
WELLINGTON A/C British two-motored bomber and patrol plane built by Vickers.
WESCH ABSORBER A rubber-like coating for reducing radar echoes. See JAUMANN ABSORBER.
WHITLEY British two-motored bomber and patrol plane.
WOLF PACKS Groups of U-boats operating together as a unit.
X-BAND Band of radar frequencies with wavelength approximately 3 cm.
ZIGZAG Frequent course changes to make attack by submarines more difficult.


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Transcribed and formatted for HTML by Rick Pitz for the HyperWar Foundation