I didn't invent this but I'm helping my friend spread the word on it (no pun intended).
Laughterbate
The act of breaking out into giggling or laughter when in the presence of noone or without external influence.
Possible uses:
That guy in the end cubicle is laughterbating again.
I see that you're a regular laughterbator.
How many times a day do you laughterbate?
Stop laughterbating, I'm trying to talk to you.
Pass it around. - The origin of the word is from a gentleman named Robert Pritchard - you can leave feedback for him on this blog posting.