acronym for FUCKING IDIOT LIAR. A person who openly makes up stories and lies to you, but is ridiculously idiotic and so doesn't understand your superior intellect knows he is lying to you.

FIL - yeah bro, I want to discover black matter, I'm way into physics.

smart guy - I think you mean 'dark matter'

FIL - yeah, thats what I'm talking about, black matter. Dude I got my masters in Physics, I'm brilliant!

smart guy- wow, I think I need to go.

FIL by bigbinthehizzy July 29, 2009

Fil

A phenomenon originating from LastNite.org. A hipster troll known to be on the cutting-edge of popular message board culture. However, he comes off as an arrogant rich prick primarily because he's an asshole who does nothing but feed on the controversy he has created.

-Hey did you hear Fil won Most Influential Poster on LastNite.org?
-Yeah, but in the interview he's a conceited prick. Im not looking forward to his next bloated self-indulgence.
-Oh, I guess you're right.

Fil by Filliam Lardass IV December 27, 2004

Fil

An adult (chick or dude) who is sexually attracted to young children; PedoFil.

The pedoFil had to register as a sex offender when he was released from Prison.

Fil by FilNation October 26, 2011

fil

n. a dork, loser or idiot. Taken from 'fool'

"That guy's a fuckin' fil."

fil by shish September 1, 2004

FIL

abbreviation of Father-in-law; often used in internet conversation

My FIL is flying down to see my husband and me this weekend.

FIL by TweedyChic March 27, 2005