Synonyms for knock out

verb

1. To make unconscious or exhausted

   put to sleep, stupefy, anesthetize, exhaust; see deaden 1, drug, tire 2.

2. To strike down

   strike senseless, render unconscious, knock one out of one's senses, knock down for the count*, knock cold*, kayo*, KO*, knock for a loop*, put a silencer on*, put out like a light*, flatten*, lay out*; see also beat 2, defeat 3, hit 1.