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3.
Acronym for Fear of Sobering Up. Someone who has FOSU may begin their drinking with Bloody Mary's over breakfast just to ensure they're never sober.

People suffering from FOSU often use boring people as a reason to get drunk in the first place.
Reginald: Dave, I'm hungover.
Dave: Hair of the dog, mate.

Reginald: Yeah, fair enough... Can you fix me a Bloody Mary or a Gin and Tonic? I don't wanna be sober around these other asshats.
Dave: Bro, you've got a hardcore case of FOSU.

Reginald: Yeah, but have you been trapped in a conversation with Betty or Rachael recently? It's like listening to an orchestra of cats.
by Springbok27 January 09, 2011
 
1.
A slightly abbreviated way of saying "for sure." Used in all contexts where "for sure" might be used.
Guy: Hey man, I heard that chick's ham wallet was vajazzled. Would you still hit that?

Man: Fo su!
by Diesel7777777 March 25, 2010
 
2.
Someone with chinese eyes and a lot of freckles.
1. "Oh man, look that guy, is so fosu"
by Camel cool May 03, 2010