One day,when i was chatting with my friend,he said "lmao",i didnt know what does it mean,he told me it was:laghing my as off.

But i dont know what does" laughing my as off" mean either.....Emotion: sad
"laughing my ass off" means to laugh very very hard.

Here "ass" refers to the buttocks, in American slang. So the literal translation for this would be "laughing till my buttocks fell off". Of course that isn't true, and I think it might have come from the more widely accepted usage "laughing my head off", which means the same thing.

So, Titi Bo, next time you post a joke and someone says "LMAO", that means "It's very funny, and I'm laughing very hard".

Hope that helps!

- Joy
Ass, not as. Laughing extremely hard.
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oh thanks

what does "ass off" mean?
 Tearsofjoy's reply was promoted to an answer.
I used to say "lmao" and similar myself, when playing online.

Shorthand for Laugh My A** Off, LMAO is commonly used in chat rooms and text based communications. Another common alternative to LMAO is LMFAO and LMMFAO, which is short for Laugh My F**ing A* Off and Laughing My Mother F**ing A* Off.

Courtesy of http://www.computerhope.com .
Hope this helps.
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See this previous version of the same question: GMBO
Well I see this as some kind of impolite.