Badunk Share definition Flag 1. The sound a large piece of feces makes when it hits the water in a toilet bowl. 2. A large lump of feces. Person 1: Why were you in the bathroom so long? Person 2: I just badunked. *Grunt*...*Badunk* Badunk by Scott Fincher October 5, 2005 0 0 Get merch Get the Badunk mug. Buy Now — $32.95 See more merch