This is the name for the sexual position that entails a girl giving a guy oral sex while he is straddling her neck. While she is busy sucking the guy's dick, the guy then proceeds to shit on her neck or chest.
Person 1 "Did you here that Jimmy took a shit on his girlfriend's neck this weekend while she was giving him a blowjob?"
Person 2 "Oh, you mean they did the meat grinder!"
Person 1 "Meat grinder, what is that?"
Person 2 "The meat grinder is when you are fucking a girl's face and you defecate on her neck."