See more synonyms for knockout on
  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, especially 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. Machinery. a device for knocking something loose, as finished work from a lathe chuck.
  1. that knocks out: the knockout punch.

Origin of knockout

1810–20; 1935–40 for def 4; noun, adj. use of verb phrase knock out Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for knockout

blow, kayo, KO, TKO, smash, looker, success, beauty, belle, sensation, eyeful, stunner, vision, gem

Examples from the Web for knockout

Contemporary Examples of knockout

Historical Examples of knockout

  • There's a knockout comin' to the best of 'em, if they hang to the game long enough.

    Shorty McCabe

    Sewell Ford

  • It was the seventeen-course night dinners and the foreign cooking that gave him the knockout.

    Shorty McCabe

    Sewell Ford

  • If Jim has told you that I gave him a knockout to win the race, it's a lie, Pen!

    Still Jim

    Honor Willsie Morrow

  • It's a blow below the belt, but it's a knockout for the moment.

    The Root of Evil

    Thomas Dixon

  • Those who had charge of the boxing never let a bout go to a knockout.

    In the Flash Ranging Service

    Edward Alva Trueblood

British Dictionary definitions for knockout


  1. the act of rendering unconscious
  2. a blow that renders an opponent unconscious
    1. a competition in which competitors are eliminated progressively
    2. (as modifier)a knockout contest
  3. a series of absurd invented games, esp obstacle races, involving physical effort or skill
  4. informal a person or thing that is overwhelmingly impressive or attractiveshe's a knockout
verb knock out (tr, adverb)
  1. to render unconscious, esp by a blow
  2. boxing to defeat (an opponent) by a knockout
  3. to destroy, damage, or injure badly
  4. to eliminate, esp in a knockout competition
  5. informal to overwhelm or amaze, esp with admiration or favourable reactionI was knocked out by that new song
  6. to remove the ashes from (one's pipe) by tapping
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for knockout

also knock-out, in fighting, 1887, from verbal phrase knock out "to stun by a blow for a 10-count" in boxing, short for to knock out of time; see knock (v.) + out. Slang meaning "attractive person" is from 1892. To knock oneself out "make a great effort" is from 1936.

Online Etymology Dictionary, © 2010 Douglas Harper