It is an abbreviation "big fat asses." A group of girls consisted of Samantha, Nicole, and Dianne. However, Nicole has the biggest one of all, and Dianne has a deflated pancake as a behind. They are very odd and laugh about the man in your eyes. Also known as bfuts extended.
"Why are you losers always together?"
Dianne: WE'RE BFA'S BITCH!
Nicole: S MY D!
Samantha: Let's go bowling!