He act of sticking a mans penis partially inside a woman's asshole while she has explosive diarrhea all over the mans dick. Causing a fountain like affect as the liquid shit drips down his dick.
"Man, I really wish I could of given her the chocolate fountain, but Joe did it first."
When having anal sex with another man, you position him so his anus is facing the ceiling. After you climax, pull out quickly, causing feces to rush out towards the ceiling creating the chocolate fountain. Bonus points for receiving a facial from the fountain.