Originated from the abbreviation KOS "Kill On Sight"

It's a word in online video games used to refer to people who are KOS.

It is more commonly used in the online game Roblox.
Dude, that koser just killed me for no reason.
The kosers are killing everyone.
i'm hackin all of you stopid kosers,
by Mr.Koalas April 25, 2020
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When you go to the bathroom to take a shit and instead of it being enjoyable. it feels like the world is ending if only the smell dosent take you first.

It may often splash up, as a final "fuck you" which makes the wiping process that much worse.
X:Dude I dont know what i ate last night but I just dropped a koser and am still surprised im here.

Y: Yeah man, those really can ruin not only a day but a week.
by Gern-haha December 13, 2010
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-you suck
-oh fuck you, you KOSER
-*loser
by nick_fox February 20, 2020
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for something to be nasty, not right or just something you wouldnt do
oh my goodness did you see her nappy hair, i swear that aint koser
by chanae November 22, 2003
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supa swaggggers
Kosers are the swaggiest family, especially the eldest daughter, Ems
by saltytoess September 13, 2021
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