Piston Slap Share definition Flag The act of fuckin a loose hoe, whose pussy is so loose a man's crank will slap around in it. When I was fuckin Cathy i suffered from piston slap. Piston Slap by Paul Trahan April 21, 2003 0 0 Get merch Get the Piston Slap mug. Buy Now — $32.95 See more merch