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Synonyms

KO

American  
[key-oh, key-oh, key-oh] / ˈkeɪˈoʊ, ˈkeɪˌoʊ, ˈkeɪˈoʊ /
Or K.O.,

noun

plural

KO's

  1. a knockout in boxing.

verb (used with object)

KO'd, KO'ing

  1. to knock unconscious, especially in a boxing match; knock out.

KO British  
/ ˈkeɪˈəʊ /

verb

  1. a slang term for knock out See knockout

"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

noun

  1. a slang term for knockout

"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

Etymology

Origin of KO

First recorded in 1920–25; initial letters of knock out

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

During the past several years, Brush has suggested KO, UTZ and HSY in his stock newsletter, Brush Up on Stocks.

From MarketWatch • Feb. 7, 2026

Beverage giant Coca-Cola KO -0.43%decrease; red down pointing triangle , with its global footprint and growing focus on zero-sugar drinks and energy beverages, also fits the mold of a steady performer.

From The Wall Street Journal • Dec. 21, 2025

"We got Justin the good look and KO got the rebound and put it back."

From Barron's • Nov. 12, 2025

American legend Marvin Hagler survived some vicious bouts, notably his 1985 war with Thomas Hearns, before retiring without a losing KO on his record.

From BBC • May 8, 2024

And you never want Daddy to go for the KO.

From "The Hate U Give" by Angie Thomas

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.