phat donkey Share definition Flag A girl with a big phat ass, that you can't resist staring at it whenever shes around you. Hey bro check out that girl over there with the phat donkey, I wanna saddle up and ride! phat donkey by GhostWritter May 18, 2014 0 0 Get merch Get the phat donkey mug. Buy Now — $32.95 See more merch