Source : WordNet®

knock out
     v 1: eliminate; "knock out a target"
     2: knock unconscious or senseless; "the boxing champion knocked
        out his opponent in a few seconds" [syn: {knock cold}, {kayo}]
     3: destroy or break forcefully; "The windows were knocked out"
     4: overwhelm with admiration; "All the guys were knocked out by
        her charm"
     5: empty (as of tobacco) by knocking out; "knocked out a pipe"