The act of jacking off with ones own shit.
I stress that you use your own shit because using someone elses....would just be gross.
After taking a huge shit, Jason gazed down into the toilet. The sight and smell of his huge fecalload caused a stirring in his loins that he could resist no more. He gave into his temptation and reached into the bowl. In his hand his shit felt warm and sensuous. Using his shit he began to stroke his throbbing fuck stick faster and faster finally bringing himself to a climax. Spent and stinking he stared down at his Chocolate Charlie.