Basically an extention of 'bro', which is an abbreviation for brother. Used when greeting another friend or comrad. It can replace words like brosef and brosky.
Appropriate mainly when you're jsut dickin' around with other bros.
Friend 1: Hey, what's going on ya dick!
Friend 2: Not a lot brostafa! Wanna get laid!
Friend 1: Right on!
Is a slang word for Brother. Except it has the ending of Mu-stafa meaning the chosen one.
Combined they create the word Brostafa. Meaning one of your brothers/best friends who you look up to for there spuriousness.
Me: What's up brostafa?
You: Wow what a compliment I didn't know i was so looked up upon by you.