runny mustard Share definition Flag After you have sex and you pull your penis out of your condom and the stuff inside spills out onto your partners pubic hair. Aww, sweetie i let some runny mustard get into your hair patch. Go take a shower. runny mustard by hexicon September 12, 2006 0 0 Get merch Get the runny mustard mug. Buy Now — $32.95 See more merch