mouth fart Ask Urban Dictionary about mouth fart Share definition Flag The sudden expulsion of air that shoots through your closed lips when someone says something really funny or really stupid. Bimbo: I think I'll run for president Normal Person: Pfbtpfbtpfbt!!! You just made my mouth fart. mouth fart by mouthfart April 17, 2006 0 0 Get merch Get the mouth fart mug. Buy Now — $32.95 See more merch