pissass Share definition Flag when you pee in a toilet before shitting. Then, when you do defecate in said toilet the pee water splashes up and smacks your bum. I just peed and shat in that order and got a major case of pissass all up in there, like dayummmm! pissass by katienedsfilthyfilms July 27, 2010 0 0 Get merch Get the pissass mug. Buy Now — $32.95 See more merch