wet (one's) pants
1. Literally, to urinate while wearing one's clothing. I had to go to the bathroom so bad that I'd nearly wet my pants by the time I made it home. Sarah has just finished potty training, but she still wets her pants from time to time.
2. To laugh hysterically or uncontrollably. (Usually used in the continuous tense.) Raj's new boyfriend is hilarious, he had us wetting our pants through the whole lunch!
3. To be extremely excited or giddy. (Usually used in the continuous tense.) Abigail and I were wetting our pants with excitement waiting for the concert to start!