dud

Etymology

From Middle English dudde (“cloak, mantle, kind of cloth; ragged clothing or cloth”), from Old English *dudda (attested only as personal name Dudda, part of modern English Dudley), akin to Old Norse dúði (“swaddling clothes”), Low German dudel. Possibly borrowed from the Old Norse word and related to dyja (“to shake, tremble”).

noun

1. (informal) A device or machine that is useless because it does not work properly or has failed to work, such as a bomb, or explosive projectile.
   The only amusing highlight was Gudgeon having managed to exploit U.S. codebreaking efforts to ambush and destroy the submarine I-173, albeit not for the lack of the Mark 14's trying to sabotage the effort, as the torpedo that had hit the sub had refused to detonate; it seemed, however, that the car-crash levels of kinetic energy involved in the dud simply ramming the sub had nonetheless done enough to fatally damage it. 29 December 2021, Drachinifel, 21:03 from the start, in The USN Pacific Submarine Campaign - The Dark Year (Dec'41 - Dec'42), archived from the original on 2022-07-19
2. (informal) A failure of any kind.
   1. (informal) A loser; an unlucky person.
   2. A lottery ticket that does not give a payout.
3. (obsolete, informal) Clothes, now always used in plural form duds.