BFYM 

1) A national organization of massaginists who use this acronymn to insult society with an inside joke known only to other members. The letters stand for:
Butt Fuck Your Mother

Secret group of male members who think everyone should, can or will BFYM.

BFYM by jrh5356 April 19, 2005

BFYM 

but fuck your mother

to have sexual relashions with your mothers ass

BFYM by NATAS May 13, 2005