Means "F*ck It Senior Year" of High School.

Strictly for senior use ONLY.
Stupid sophomores try to Disguise it as Fi Sophomore Year
But they are just trying to be cool. And Failing.
Senior One: I got so drunk last night I don't even remember!
Senior Two: Dude me too!
Both: FISY!!

Sophomore: FISY
Seniors: *Jump the sophomore*
by carebear sheep April 24, 2011
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Term used in Kenya to describe a man who is always chasing skirts.
That dude is such a fisi. He is always running after some girl or other in the office.
by mmassive December 21, 2018
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