Boonkey Share definition Flag Commonly used in Charleston, SC. It means butt (derriere). Boonkey is a Gullah/Geechee word. Gullah/Geechee: "Gaaareed dat gurl dere got a big ol' boonkey on she!"Translation: Wow, she has a huge butt! Boonkey by dmwinthrop May 4, 2010 0 0 Get merch Get the Boonkey mug. Buy Now — $32.95 See more merch