This is when two partners are engaged in a form of anal sex. At the appropriate moment "typically when you could toss a quarter down their gaping asshole" you perform the Reverse Mudslide. While in the piledriver position the partner on top will pull out and proceed to shit directly into the gaping hole of their partner thus completing the reverse mudslide. While diarrhea is preferred a nice corn filled shit will work quite well. Speed, accurancy and patients are the key to pulling this one off.
Hey Sally be sure you're light on the cheese in the casserole tonight. I want to keep things loose so we can pull off the Reverse Mudslide tonight.
Dorothy is a true believer that the reverse mudslide is the perfect way to finish the ever famous pile driver.