Stands for "What the Bro" - A derivation of normally vulgar terms such as What the Fuck, What the Hell or What the 'Zad. Used in reference to a situation where one gets "bro'd", the male version of "hoe'd". Can be used in any context whenever a bro gets shat on, whether it is a light shat or heavy shat. Term originated in Houston, Texas and is increasingly becoming popular in the South.
You went to the game with a P instead of me? WTB? I don't know what the bro you broin about, but you need to bro the bro off, bro!