FOS 

Father over shoulder.

Stop the cybering! FOS!

FOS by AriBigFatBlackGuy November 30, 2009

fos 

it could mean also :

Free Open Source

fosdir.com

mean

Free Open Source Directory

fos by peter edin October 16, 2008

FOS 

1) Friggin' Awesome Shit.

2) Friggin' Awful Shit.

meaning varies according to situation. yeah, it doesn't make sense, but at least 2 or 3 people I know have used it.

FOS by bastardface October 21, 2004

FOS 

FOS pronounced as False. Meaning Full Of Shit, some one who tell obvious lies to exaggerate there lifestyle.

Alvin so FOS. Why he trying to impress me with all them lies?

FOS by TheRealKennis March 11, 2017

FOS 

Fucked over sink

Don’t you just hate when you play fortnite and your mom gets FOS’ed by some random guy

FOS by cw91fos May 13, 2018

FOS 

Full of shit.

That pillow lady, was FOS, with all her constant hypocritical judgments.

FOS by Hot Chicky Babe January 31, 2020

FOS 

FreedomOfSpeech

Rampage FOS!

FOS by TrumpTheKiđkissingSexoffenđer. November 22, 2020