When you have such a fibrous diet that you're able to poop directly into someone else's asshole. Typically used in a sexual manner, occasionally as a threat.
The unfortunate result during anal sex if the person doing the receiving does not properly prepare for the event, ie douching with a colonic or an enema, something, ANYTHING, for God's sake.
His date knew that anal sex was going to happen, but failed to prepare, and after a few minutes a Malibu Mudslidecut their evening short.
A sexual act, the milwaukeemudslide occurs when the female defecates loose stool onto the partners chest while riding him reverse cowgirl.
Last night Misty went to dinner, ate some really spicy food and went home to have sex. She felt her stomach rumbling so she urgently asked me if I would like a milwaukee mudslide. I was more than happy to receive it.