[kill.er] n (15c) 1: one that kills
2: killer whale 3 a: one that has a forceful, violent, or striking impact b: one that is extremely difficult to deal with
[2]killer adj (1951) 1: strikingly impressive or effective "a ~ smile" "a ~ resume"
2: extremely difficult to deal with "a ~ fastball"; also: causing death or devastation "a ~ tornado"