1. when something happens that leaves u with absolutely nutin to do but for your two nuts to (imaginatively) knock against each other
2. bangin' balls - the act of above
3. bang balls also means a fuck-up. for example when something happens not in your favour, or something embarassing happens to u, u can say "bang balls man!"
usage 1 - "yo bitch left me bangin balls, she ditched me midway and hit d clubs downtown! puta!"
usage 2 - "shit, the whole bar was watchin me drink d flaming, and i had to fry my fuckin eyebrows man!"
"Shiiit man, really?! haha! dats a major bang balls, bitch!"
When the drunk bitch at the bar comes up to you while you're conversating with possible bone down. And ends up scattering everyone away and leaves you stranded without ass.
Joe was just about to get two chicks in the bag before ole flashbang came over.