To Bang off is to ride or die for someone. The same idea as 50/50. Means I ride for you, you ride for me. Usually said when giving someone dap and pointing the index finger at them instead of keeping a closed fist. It's a symbol that you're really cool with someone, cool enough to ride for them. If you don't do that to someone or they don't do it back to you it's not disrespect, it just means they don't mess with you like that and that it's just a formal/polite shake.
1. Aight soldier, I'm outt, Bang Off.
2. That's my nigga Justin, it's Bang Off for him.
3. I Bang Off for my brother.