Rectal Grenade

feces, shit, crap, turd, dung...whatever else you would like to refer it as.

"I just about blew the toilet up when I tried to flush that rectal grenade."

"If you don't shut the hell up, I'm going to hold you down and drop a rectal grenade in your mouth!"

"I just had the biggest rectal grenade come out...now my butt hurts"