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1.
Like LOL, but cooler. LAUGH UNTIL I SHIT MYSELF.
"Hahaha OMG that just made me LUISM!"
by CooCooz. April 21, 2010
 
2.
1)To make an accidental innuendo without realising it in general conversation.
2)To fall over in a hilarious manner.
1)Katie: Then we should shoot all the blondes!

Louise: Can I keep them all afterwards? I love blondes.
Katie:....Necrophiliac!

Louise: I didn't mean it like that it was a total Lu-ism

2)Penny: Did you see Janie just fall of that seat over there, it was hilarious. Best lu-ism from her YET!
by g0ldengirl June 13, 2009
 
3.
When someone makes a typo in chat
WHen I wnrt to the store today, I bought some ,ilk.. Is an example of Luism
by LuLunsford June 04, 2009