BMF for short. The faceless blue MSN figure that annoys the shit out of anyone and everyone by either:

a. Turning the whole chatbox bright orange if you're using Windows, or:
b. Zipping around like a total shit-eater if you're using Mac, effectively blowing your cover of pretending to do your homework while chatting if your parents happen to pass by.
Mom: Son, what are you doing?
Sam: The English essay. I've written five hundred wor-
Icon: Bla-ba-bam!
Mom: Glares.
Sam: ... Damn you, Bloody MSN Fucker.
by Beastly Cock March 29, 2010
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