Poocelain Share definition Flag Commonly known as a skid mark, this is a poo-stain than has unforgivably transpired onto the porcelain backboard of the toilet. Your Dad: I've left some bad Poocelain back there. You: Get a grip Dad. Poocelain by PeeledWig June 11, 2016 0 0 Get merch Get the Poocelain mug. Buy Now — $32.95 See more merch