The act of walking around nervous that an unsuspectingfart may be the one loaded with a diarrhea bullet. Not to be confused with a shart, this is a full blast of watery shit that will ruin undergarments.
"I ate 20 hot wings last night and drank shitty beer." "I walked around playing diarrhea roulette all day, until the chamber had one in it." "I had to throw the underwear out!"
When you go take a dumb/crap/shit and your shit hits the water hard enough so the water ends up going up and the water touches your ass.
Bob: Well my day is ruined!
Jack: Why?
Bob: I had reverse diarrhea
Jack: wtf is that?
Bob: Its when you go shit and your shit lands in the water really hard and the water splashes against your ass.