a shorten version of the word "MO", which is a shortened version of the phrase "MO-FO", which is also shortened for the term Mother
Fucker.
Basically it's a quick and
easy way to call someone a mother
fucker without having to use all those syllables.
"You are such an MMF!"
Jason: Hey guys!
wow you look like crap today, well i gotta run BYE!
Todd: What is that
guy's problem?
Gilroy: I don'
t know dude, i guess he is just an mmf