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"Must be following" on Tumblr; maybe even Twitter.
First 20 to reblog will be promoted. MBF (inserttumblrnamehere).
by sophiechloe January 07, 2012
Acronym for Metro Best Friend
Yvi: Who's that guy over there with the v-neck?
Christine: That's just my MBF, JP.
by TheJBCrew April 10, 2011
An acronym for "Milky Bum Factor"

Anal perspiration caused by hot and humid conditions. Leaves one's bum feeling moist an unclean. The higher the MBF factor, the worse the milky bum feeling is.
Seriously, it is so hot & humid outside i think the MBF is at 9.5 today.
by awefsvc July 14, 2010
The term used between close friendships. MBF stands for Mega Best Friend.
Dylan: Hey you're my MBF
Mariam: You're my MBF too!
by mari__ December 26, 2013
Abbreviation for "must be fried." Said when someone says something so ridiculous, they must have been fried.
you- OMG i wanna see that movie! i had a dream i saw it, but i never actually saw it... this is like SO much fun!!!!!!!
me- damn you MBF.
by NPENN GETS FRIED February 22, 2011
A boy friend acquired while vacationing in Mexico, preferably of Mexican descent.
Sally: What was that noise last night?
Rose: Oh that was just my MBF climbing through our kitchen window.
by SquirrellyB July 26, 2010
Missionary Butt Fuck
Sarah: Oh my G I hurt so bad.

Jessica: Why's that?

Sarah: Well I let Steve missionary butt fuck me (MBF) and now I am afraid I will have to steal some of my grandma's diapers so I don't shit my pants.
by two lips May 18, 2010