From Longman Dictionary of Contemporary EnglishU-boatU-boat /ˈjuː bəʊt $ -boʊt/ noun [countable] PMNa German submarine, especially one that was used in the Second World War
Examples from the Corpus
U-boat• You know enough about that to know the difference between a whale and a U-boat?• They acted as bait and, once a U-boat surfaced, could out-gun her.• You know what a U-boat looks like, boy?• Mina got the tip-off just in time and they became U-boats, went underground.• The convoy was attacked by U-boats during the night of March 16-17 and 12 ships, including Southern Princess, were sunk.• There is no mention of U-boats or the Luftwaffe.• They already seen U-boats off Nova Scotia.• Then the U-boat just left them on the open seas.Origin U-boat (1900-2000) Translation of German u-boot, from unterseeboot “under-sea-boat” 