a guy sees a girl walk past who has an extra fine ass and says to his mate
guy-"i wouldn't mind putting my thumb in that"
mate-"yeah thats what i call a badonkadonk"
A womens derriere that has the shape of, and bounces like a basketball. The word is derived from the sound produced when you bounce a basketball. A case of the sound of one urban icon, naming another urban icon with similar propensities but that doesn't really make a sound.