BFSM 

Best friend soul mate. This term defines two people who were meant to be, and always will be best friends. More important than best friends, bf, gf, bff ect ect...

Muh BFSM be the shit. always and forever

BFSM by bw77 January 18, 2010

BFSM 

Standing for "Best Friend Soulmate", it is a term used to describe a person as someone you're destined to be best friends with.

Person A: OMG! Michael's so cool!
Person B: I know he's just like you
Person A: He's like my BFSM!

BFSM by Penelope S. May 27, 2013