While it might be clever of you to suggest that quondam describes anyone who tells you nothing is impossible -- and you respond by asking him or her to dribble a football. On second thought, perhaps it's just a politically-correct description for a potent piece of pop-out paraphernalia. Who knows, the latter answer may get you the booby prize!
Actually, quondam is a rather eloquent term meaning, belonging to some prior time. Synonyms: erstwhile, one-time, sometime, former, old.