A medical condition in which your anus becomes inverted. Often comes from too much anal sex. Other causes may be extreme internal pressure over extended periods of time, prolonged diarrhea, or prolonged constipation.
Shit dude, I just fucked this chick's asshole so hard I gave her an anal prolapse, and I was like "lol, wut?"
When the rectum protrudes from the anal cavity. This can either be a result of sodomy or over exerting one's self while defacating.
Did you see that red blob come out of that chicks ass while she was shitting on his face?!?!? She's got an anal prolapse.