the REAL definition is this: a man is giving it to a girl from behind. he then pulls her up by the legs and knocks her arms out from under her. He then proceeds to drive her across the carpet on her face like a snow plow.
I gave Cindy the snow plow last night, and her tits are STILL red!
After shooting a wad on the face of a woman laying on her back this is the motion of rubbing the scrotum and ass back and forth across her chin and face.
To let Mary know the relationship was over John finished his business and proceeded to give her a Pittsburgh plow.