When you're fucking a girl in the ass, and when you're about to go, you knock her arms out and fall down on her.
Brian told Derek to snow mobile that bitch.
When doing a girl from behind, you sweep her arms out from under her so that her head hits the floor. You then grab her wrist, pull her arms behind her back and act like your stearing a snowmobile.
That @sshole Chuck was making stupid motor sounds when he gave me a snow mobile last night.