ttid
ttid stands for "titter til I die", and since titter already stands for something that is funny, the word can be used for when you see someone totally doing something hilarious. This word is like an LOL and since that is overly used a new one like TTID can be used.
I love to ttid when my friend makes an awesome joke.

I was jumping on my trampoline with my friend Alexandra and all of a sudden she fell off, ttid!