knock-out

CIDE DICTIONARY

knock-out, a. 

 That knocks out; characterized by knocking out; as, a knock-out blow; a knock-out key for knocking out a drill from a collet.  [Webster 1913 Suppl.]

knock-out, n. 

•  Act of knocking out, or state of being knocked out; the act of rendering a person unconscious by a blow.  [Webster 1913 Suppl.]
•  a blow which causes a person to become unconscious.  [WordNet 1.5]
•  the winning of a boxing contest by rendering the opponent unable to stand for a specified period, usually a count of ten; -- in contrast to a win by a decision; as, Muhammed Ali won by a knockout in the first round.  [WordNet 1.5]
•  a strikingly beautiful woman.  [PJC]