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1 definition by Ilovecurry

 
1.
FOS
Fuck On Sight. An acronym used by two friends to describe a person who they see who they would like to instantly fornicate with on sight.
Two guys are walking when they see a really hot gurl and one gay says to another FOS? And the other gentleman nods in unison.
by Ilovecurry April 14, 2010