KO

or K.O., k.o., kay·o

[ noun key-oh, key-oh; verb key-oh ]

/ noun ˈkeɪˈoʊ, ˈkeɪˌoʊ; verb ˈkeɪˈoʊ /

Slang.

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See synonyms for KO on Thesaurus.com

noun, plural KO's.

a knockout in boxing.

verb (used with object), KO'd, KO'ing.

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

QUIZ

ALL IN FAVO(U)R OF THIS BRITISH VS. AMERICAN ENGLISH QUIZ

There's an ocean of difference between the way people speak English in the US vs. the UK. Are your language skills up to the task of telling the difference? Let's find out!

Question 1 of 7

True or false? British English and American English are only different when it comes to slang words.

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Origin of KO

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

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use KO in a sentence

“Gronkowski” itself never manages to sound more erotic than the name of a hearty Polish stew or a D-list WWE performer.
‘A Gronking to Remember’ Speed Read: 8 Naughtiest Bits|Emily Shire|January 7, 2015|DAILY BEAST
I take calcium and vitamin D supplements, but prescription medications are generally only for women in menopause.
You’re Never ‘Cured’ of an Eating Disorder|Carrie Arnold|December 20, 2014|DAILY BEAST
Then Pascal responds (in all caps) with, “BUT WE DIDNT WIN A D [sic] YOU KNOW HIM.”
Exclusive: Sony Emails Blast David O. Russell For Allegedly ‘Feeling Up’ Transgender Niece|William Boot|December 14, 2014|DAILY BEAST
The move gets an “A” for symbolism and a “D” for everything else.
Sony Blames North Korea for Hacking, but Washington Left Them Completely Vulnerable|Gordon G. Chang|December 3, 2014|DAILY BEAST

Sen. Claire McCaskill (D-MO), a leading voice on police demilitarization, was supportive of the White House announcement.
SWAT Lobby Shoots to Kill Police Reform After Ferguson|Tim Mak|December 2, 2014|DAILY BEAST
C was a Captain, all covered with lace; D was a drunkard, and had a red face.
Boys and Girls Bookshelf; a Practical Plan of Character Building, Volume I (of 17)|Various
D'o l'on peut aussy veoir, quelle esperance il y a de planter une belle chrestient par tels evangelistes.
The Jesuit Relations and Allied Documents, Vol. II: Acadia, 1612-1614|Various
Neither of us spoke again, and at length the squat log buildings of Pend d' Oreille loomed ahead of us in the night.
Raw Gold|Bertrand W. Sinclair
He picked out that simple little study of Cramer in D major in the first book—you know it well—and asked me to play it.
Music-Study in Germany|Amy Fay
(d) Excess balances may, at the convenience of each federal reserve bank, remain deposited with the gold settlement fund.
Readings in Money and Banking|Chester Arthur Phillips

British Dictionary definitions for KO

k.o.

/ (ˈkeɪˈəʊ) /

verb KO's, KO'ing, KO'd, k.o.'s, k.o.'ing or k.o.'d

a slang term for knock outSee knockout

noun plural KO's or k.o.'s

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