scum mouth Share definition Flag Adj. The smell of morning breath mixed with unswallowed cum from the night before This morning, in bed, I leaned in to give a sweet kiss, but was repulsed by the smell of Scum Mouth coming from their lips scum mouth by KJH22 May 31, 2016 0 0 Get merch Get the scum mouth mug. Buy Now — $32.95 See more merch