Definitions by Gygaxis

JFYM 

JFYM is an acronymn that stands for "Just Fucked Your Mom"

Oh man... I hate to break it to you but, I JFYM...

or the alternate Just Fucked My Mom form
WTF MAN!?!? DID YOU JFMM?!!! I'M GONNA KILL YOU ITCH

JFYM by Gygaxis June 3, 2004