1. An unpleasant or incorrect musical note. Oof, that was a real clinker—my finger slipped and hit the wrong key.
2. Someone or something deemed to be insignificant or ineffectual. I think it's time for me to get a new car—this one has turned out to be a real clinker.
clinker
1. n. a mistake; (in music) a misplayed note. Look at the score, man! That series of clinkers just isn’t there.
2. n. a worthless person or thing. (From the term for a cinder.) Ralph has turned out to be a real clinker. We’ll have to pink slip him.