Butt Barf 

a watery, chunky substance that is excreted from the anus in violent bursts

That mexican food gave me a wicked case of butt barf.

Butt Barf by Feason May 10, 2006

butt barf 

Another name for bad diarrhea. Especially if there is a lot of it and it comes out with a lot of force, causing you to bend over and strain a lot, almost like you are dry-heaving or about to barf. But you do it out your butt instead of your mouth. Butt barfing.

Man, what is up? I heard you in the bathroom and it sounded like a waterfall in the toilet?

Uhhhhh, sorry dude... I had major butt barf. Might not want to go in there for a while.

butt barf by offya January 3, 2012