1. n. a knockout. (The abbreviation is an initialism. Boxing.) It was a quick KO, and Wilbur was the new champ.
2. tv. to knock someone out. (see also KOed. Boxing.) Wilbur planned to KO Wallace in the third round.
1. mod. knocked out. (Initialism. Originally from boxing.) Wilbur was KOed and got a cut over his eye.
2. mod. alcohol or drug intoxicated. (Initialism.) Both guys were KOed and spent the night.