Source : Webster's Revised Unabridged Dictionary (1913)

Knock-out \Knock"-out`\, n.
   Act of knocking out, or state of being knocked out.

Knock-out \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.