Its etymology is derived from countless & careless amounts of sexually sadistic encounters with VERY fat, VERY ugly, VERY smelly and SUPER HORNY OLD women (named Barb & Joan) who are adamant about getting cock-slapped across the face CONSTANTLY. I mean CONSTANTLY.
These two women have single handedly shaped the way we think about extreme sex and/or sexual domination. So, you ask, what exactly is a BarbJoan aka BJ? As of 2012, it's the NEW standardized unit for molesting/torturing an elderly woman beyond your physical threshold, while still maintaining an enjoyment level for her. Yes people, she has to be THAT MUCH of a whore.
However, there are 2 important things to remember:
1) You cannot call a sexual act a BarbJoan unless the chic actually enjoys getting annihilated and enjoys physical pain.
2) If you aren't sweating, it's not a BarbJoan so try harder.
"Dude, omfg, that BarbJoan was AMAZING last night. The dumb bitch turned her head and I broke my hand with the brass knuckles, though.."