the tendency of back seat belts of newer model cars to continually adjust throughout the ride, slowly constricting the victim like an anaconda. This is more prone in overweight individuals, which leaves the belt pressed into their fat approximately 1 inch. The only solution for snake belt is to undo the belt and start the process over again.
Frank: "How long till we get to Chik-Fil-A. I've got a crazy case of snake belt going on back here."
Alex: "Just undo it and start over. You don't wanna end up like Jon Voight."