n. (informal)
25B6; noun their new product is a dud : FAILURE, flop, let-down, disappointment; Brit. damp squib; informal washout, lemon, no-hoper, non-starter, dead loss, lead balloon; N. Amer. informal clinker.
success.
25B6; adjective
a dud typewriter : DEFECTIVE, faulty, unsound, inoperative, broken, malfunctioning; informal bust, busted, kaput, conked out; Brit. informal duff, knackered.
a dud £50 note : COUNTERFEIT, fraudulent, forged, fake, faked, false, bogus; invalid, worthless; informal phoney.
sound, genuine.