This refers to a butt that is so badonkadonk that its degree of badonkadonk-ness is badong (both bad and wrong).
That be one badongkadonk badonkadonkey!
She way badongkadonk...
That girl badongkadonker than 47 motherfuckers...
3. Teh jelleh
Host: What...is a badongkadonk?
Contestant: Awww man...that's junk in the trunk.