look up any word, like b4nny:
 
1.
mbn
1. stands for "must be nice" and used sarcastically when someone tells you something that makes them sounds wealthy, carefree, or conceited.
Wealthy Chick: My parents, my sister and I are going to Aruba for Christmas for a week then to Argentina and Brazil to spend the New Year.

Poorer Friend: MBN! shit!!!

Wealthy Chick: What does 'mbn" mean?

Poorer Friend: it means that it Must Be Nice, mutherfucka! Tell your parents to hook ME up!
by El Muñeco December 08, 2005
 
2.
mbn
must be nice..........
GuyA: Damn I'm full, huge steak dinner.
GuyB: I'm eating chicken Ramen, mbn.
by wikked January 06, 2005
 
3.
MBN
Jackronyn for MasturBation Nation - A group of outstanding (self proclaimed) men, linked by messaging technology to share in inappropriate comments, sarcasm, and random shenanigans.
Girl A: "Look at that group of extremely hot guys texting inappropriate, sarcastic, highly intellectual messages."

Girl B: "Hot is right. I have always dreamt of being the centerpiece in an MBN circle twerk."
by justsanotherdude December 02, 2013
 
4.
Acronym for MUST BE NICE. Usually used on Facebook when someone posts pictures of a fancy car or house.
Brian: Check out my $68,000 Honda

Joey:M.B.N
by BAUWLUH August 17, 2011