an acronym for "laughing till i pee myself" describing the uncontrollable laughter that gives you the sensation of wanting to undergo micturition.
Jack, "oh shoot did u see that guy eat it?"
John, "hahaha aww man I'm gonna LTIPM pretty soon!"
LAUGHED TIL I PEED MYSELF
ALEX: WOW, "THE ROCK" IS SUPER SEXY.