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3.
(Informal Noun) a person or thing that is overwhelmingly attractive.
Svetlana knew how to dress to perfectly complement her tall, athletic frame. By virtue of her bright eyes, silky long hair, and a smile that could stop a revolution, people widely regard her as a knock out.
by JigHexadecimal August 26, 2007
 
1.
1. A very attractive woman. So named because her attractiveness is so stunning that it can (figuratively) knock you out. (make you speechless, stutter, etc.) Hence the term "knockout."
2. A punch in boxing that knocks your opponent unconscious, typically ending the match.
Guy1: Wow check her out!
Guy2: Yep, she's a knockout all right.

by GMG1 January 02, 2008
 
2.
to go to sleep. mainly said in reference to a full nights rest, 7 or more hours.
hey man, i'm about to knock out. laters.
by noooooooooope June 07, 2009
 
4.
This is a girl who is beautiful with or without makeup. Most are high matinence but doesn't mean all of them will be. She has it all, beauty and brains.

Also know as: Knockout Beauty.
I like dat chick right there! She's a knockout.
by Mon-Mon August 13, 2007
 
5.
a basketball game where one person shoots a free throw/three pointer and if he misses he must chase his ball and make any shot before the person behind him makes a shot.
I can't shoot so he beat me in knockout.
by ben renner June 22, 2005
 
6.
To go to sleep.
I'm so tired so I'm gonna knock out!
by Blabbermouth June 23, 2014
 
7.
when having sex, you go for at least three rounds that are at least 30 minutes long and you don't cum until the the third or later round
round one=no cum, round two=no cum, round three=cum and KNOCK-OUT
by Wizzard the Juggalo December 09, 2010