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1.
Fnis derived from a country in Europe called Denmark. First spotted on the streets in Madison, Wisconsin early in 2005. Used as a noun. Somewhat like a dime.
Only the pimpest of players use this term.
See also... Hottie - Dime
1. "Damn man! Did you see Eva today?! She's such a fnis"

2. "Eva, oh my god, look at Chrstian! Walkin' up and down the halls like a true fnis."
by schmidt February 17, 2005
 
2.
FNI
Friday Night In
I'd much rather drink a bottle of wine and enjoy my FNI alone.
by Pweee February 26, 2010
 
3.
fni
comes from (F)ucki(N)' (I)nsane, comes from a switch in Symantec Ghost and pretty much does nothing... hence its fucking insane.
person #1:Dude did you see that guy get hit and run over like a rabbit?

person #2:yea man, holy shit that was FNI!
by t3h-0wnz0r February 21, 2005