noun

a thing that fails to work properly or is otherwise unsatisfactory or worthless.

all three bombs were duds

adjective

not working or meeting standards; faulty.

a dud ignition switch

defective,faulty,unsound,inoperative,broken,broken-down,not working,not in working order,not functioning,malfunctioning,failed,bust,busted,kaput,on its last legs,conked out,done for,duff,knackered,buggered

verb

trick or swindle (someone).

they became increasingly aware of their rights and how much they were being dudded