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14.
FOS
this is a shorter term for "Flap Of Skin". a flap of skin is someone in your group of friends whom you may consider the "loser" or the person who you only hang around with for a certain reason, that reason not perticulary meaning you enjoy their company.

it could also mean someone with NO private parts.
" Kris has no vagina"

"She is but a Flap Of Skin!"

"I couldn't concentrate when the FOS was talking to me, she annoys me to much."
by i heart flap of skin July 12, 2009
 
1.
FOS
Abbrev. Full of shit.
by Targen December 02, 2002
 
2.
FOS
An abbreviation, meaning "fuckable-on-site". Used to classify extremely sexy people who arouse others to an immediate, uncontrollable frenzy.
Jared Leto (of 30stm) - inherently FOS. No question.
by _Jules_ December 17, 2008
 
3.
FOS
The acronym for a person who is Full of Shit. When someone is constantly telling outrageous lies, typically about themself, in order to impress others.
"Did you hear that FOS was offered a full scholarship to Harvard, but turned it down to be a UPS driver?"
by Quinn Littles May 14, 2009
 
4.
Abreviation for "Full of Shit"
You are so "F.O.S."
They are really so "F.O.S."
by Bev Lane May 29, 2006
 
5.
FOS
Full of shit
Never trust a used-car salesman, they're all FOS.
by Barbarella11 December 20, 2010
 
6.
Code word for full of shit to get you out of trouble. You say it to someone and they just look confused when other people might realize what it means. Can also be pronounced Fos for short.
When my teacher told me that my homework assignment I turned in was worth a D when I knew it was worth and A, I said "You're F.O.S., this work is flawless!" I got sent to the office because apparently he knew what F.O.S. meant.
by PrincessR December 06, 2009
 
7.
Acronym for Fuck On Sight. A type of individual when seen by another, one would be willing to have sex with without knowing anything about them, not even their name.
"Dude, that girl in the parking lot, her eyes, those hips, she's a definite F.O.S."
by mayej May 10, 2009