Pronunciation: (nok'out"), [key]
1. an act or instance of knocking out.
2. the state or fact of being knocked out.
3. a knockout blow.
4. Informal.a person or thing overwhelmingly attractive, appealing, or successful.
5. a panel in a casing, can, or box, esp. of metal or plastic, so designed that it can readily be removed, as by punching, hammering, or cutting, to provide an opening into the interior: a knockout in a junction box.
6. Mach.a device for knocking something loose, as finished work from a lathe chuck.
that knocks out: the knockout punch.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.