Its when one of your friends(who might have attention problems) become bored, and will either punch you in random spots or just make random insults. More of an annoyance, it can be treated by simply saying "bbs" and your friend will usually get pissed off at you but will halt his offensive gestures to avoid more humiliation.
Bronson: *Punches you in the arm*
Me: lol, BBS
Bronson: WTF i told you not to tell other people!! *punches you more*
Friends arond me: LOL, BBS.
Me: Don't gay guys get pms like every month like chicks?
Jason: lol no
Me: well what do they get?
Jason: BBS? only more often than a month