Brocab is short for brocabulary. Brocabulary is bro vocabulary, which is words that replace the prefix of words with the new prefix of bro. This is even the case with the actual word that is being defined.
BROmosexual(homosexual), BROcean(ocean), BROdom(Boredom), BROcab (Vocab)
by 5443564 March 10, 2008