An increasingly popular contraction that stands for "laughing in public".
Originated by the infamous underground rappers Tay T & Mar J in a collaboration with Drizzy, LIP is used commonly in chatrooms, on social networking websites, and through text. It is a subtle way to express the embarrassment that occurs after encountering something so funny that it is impossible to stifle your laughter whilst in public.
Can also be used to describe laughing at a computer screen, even and especially if you're all alone.
Often used repeatedly.
M: *Texts a picture*
T: She looks like a burrito
M: LIP LIP