This would be a large butt or booty. Has been misspelled on this website by the "urban" MTV cultured viewers. Has root in refering to a butt that would be likened to a donkey's behind, meaning that it sticks out quite a ways. Should only be used in context of describing a females abnormally large butt.
Did you see that girl who walked by? She had a badonkadonk! Damn that was a big booty