It stands for Laughing my fucking socks off.
Or also a commonly made mistake
when trying to type LMFAO.
:D
1 Person: ~tells a funny story~

2 Person: Hahaha I'm LMFSO now.

3 Person: ROFL
by iAcidic April 4, 2009
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That joke was so funny I that I’m laughing my fucking sack off (Lmfso)
by Psychoticdingus February 28, 2018
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Laughing My Fucking Sauce Off
mostly used by bros and Hockey players
Kyle-ay did you just see that plug throw that shitshow pass
Joe-Yeah pure dust LMFSO
by Jsmells June 5, 2011
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Someone references a iconic vine that’s funny
LMFSO
Someone says lmfso means laughing my fucking socks off

LMFSO absolutely not what kind of lame ass definition is that
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