piss (oneself)

1. (rude) Literally, to urinate while wearing one's clothing. I had to go to the bathroom so bad that I I'd nearly pissed myself by the time I made it home.

2. To laugh hysterically or uncontrollably. Raj's new boyfriend is hilarious. We were pissing ourselves through the whole lunch! I was pissing myself laughing at that comedy gig last night.