While doing doggy-style, you insert you thumb into the girls arse several times, with your hand in the same position as if you were throttling a motorbike
JD took that girl home, bent her over, and ended up motorbiking her!!
A pornographic act describing getting a blowjob from a girl with pigtails - holding the pigtails in each hand and pulling her head in so that she gargles on your penis, making a sound like a motorbike.
Dude, that chick will go down on anyone, she is so hardcore she is in to motorbiking!