Possbily the most annoying term that stupid college/high school guys use to talk to their friends. Its slang for bro which is short for brother. Neither of either the latter need any abreviation or slang because they're stupid terms to refer to a freind to begin with.
Frat boy 1: Yo brah dude bro you goin to the party brah?
Frat boy 2: Only if you and all my other dude brahs are there bro.
Frat boy 1: Sweet brah I'm gunna get krunk dude.
Observer with IQ greater than 4: Um try speaking english morons.