whats up bro means: Bro can be described as a brother, a mongrel or friend. It could also refer to your best enemy, if you’re feeling me. A whatsup is a question asking your enemy what’s new. You might ask a friend “Whats new”, but an enemy will use this language to threaten you. People who use whatsup bro with their friends are considered mentally and physically insane and fit only for the top security mental intitution. (in Community Dictionary, added by Abel Schroeder)