Body language taken to the extreme. A gesture used during conversation to give positive feedback in an ambiguously sexual manner.
The movement consists of thrusting your hips into the hand of your conversation partner and slightly/slowly rotating, usually paired with eye contact and a smile.
Mike: "man I was just talking to this girl and she was really into me"
Dave: "how could you tell?"
Mike: "Because we were talkin and she kept thrusting her crotch into my hand"
Dave: "Oh no man, thats just the hand hump. She does that to every guy when she's drunk"