Another contribution from the negro community, "Bust A Nut" is a typical crude euphemism coined due to the low intelligence and lack of education in the ghetto. Typically, when one ejaculates, one empties the testicles (nuts). Why one would want one's nuts "Busted" (crushed, smashed, broken), I can't imagine. It would be more accurate to say "Drain A Nut", but the typical ghetto negro would likely be unable to wrap their tongue around the two "n" sounds so close together, and the end result would be "Dranana" or something equally ghettotastic. Silly negroes. Learn to articulate and stop relying on rappers to furnish your lexicon.
Say, Tyrone. I was fornicating Tonaniquishalika last night, and proceeded to 'bust a nut' on her rather gigantic posterior. Why do us black folk like giant asses so much, anyway?