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Originating in 2006, where one person would often use his palm to cover his face then turn away saying:'AAWWWWWWW MMMMMAAAAASSSSSSS'. That same person then used the word mass as a very poorly defined insult-apparent (we all just thought he was a wackjob).

There then born was the phrase mass fat. Now used in conjunction with the mass rotation, in situations of obvious not-funess/uncool-ness/shittyness.

Also can be used as an exclaimation, or as adjective. Sometimes as a suggestive noun.
person one: Dude! The French was due yesterday!!!

person two: MASS FAT!!!

person one: Do you know Avirl Lavigne?

person two: She's mass fat.

*person one does a crappy move in soccer*

person two: You're mass fat at soccer.
by BAM! and the dirt is gone! October 14, 2007