bum shine; bumper shine verb to hang onto the rear bumper of a car and slide behind it in icy weather CANADA
It is, of course, a dangerous practice. It is usually called bum shining even though you can slide on your feet, your back, your bum, or just about any other part of your anatomy. — Chris Thain, ColdasaBay StreetBanker’sHeart, p. 27, 1987