Source : WordNet®

dud
     adj : failing to detonate; especially not charged with an active
           explosive; "he stepped on a dud mine"

dud
     n 1: someone who is unsuccessful [syn: {flop}, {washout}]
     2: an explosion that fails to occur [syn: {misfire}]
     3: an event that fails badly or is totally ineffectual; "the
        first experiment was a real turkey"; "the meeting was a
        dud as far as new business was concerned" [syn: {turkey},
        {bomb}]