Party-rrhea happens the day after a heavy session of drinking from the night before. It consists of peeing out of your butt excessively such as the popular ailment diarrhea.
Room mate 1- "come on man, I really need to get in the shower for work."
Room mate 2- "dude, i have the worst case of party-rrhea right now, you don't even wanna know, this is my 4th session."
Room mate 1 "ew."