F/O usually stands for Fictional Other, which is a term often used by Self-shippers, mainly on Tumblr.

You can have romantic, familial and platonic F/Os!
Self Shipper 1#: Yo, I got a new F/O!!
Self-Shipper 2#: That's so cool, who are they?
Self Shipper 1#: It's Peter Parker from The Amazing Spider-Man, 2012!
by enotits October 14, 2018
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Fly $hit Only
F$O 24/7!

F$O dinero
F$O Pete

F$O Kash
F$O Geo
F$O Swift
F$O Phon
F$O Twin
F$O Sauce
F$O MK
F$O Snipa
by F$O_Kid August 30, 2019
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A politician in the democratic party who does an awful job.
"Bob Casey won't support pro-environment legislation. What an f-o-crat!"
by justkindachillin April 3, 2009
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Joey: DUDE. I just mashed my thumb with the friggin hammer.

Aaron: last night, my girlfriend was blowin' me and decided to use her teeth.

Johnny: Oh shit. Apparently my lady is also my cousin...

Joey: F. O. C. L.

Johhny: Pretty much.
by Add pseudonym here July 26, 2009
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According to Nicole Liang, Cool Fobs means People who dress in clothing made and designed by asian people, and that if you "DO NOT" dress like a "FOB" then you is not cool.
Hey, Nicole......you like my new J.Lindeberg
shirt?

Pff.....no....it's not fobby.....your not a Cool *F*O*B*
by A Pimp Named SlickBack ver2 January 25, 2009
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Great underrated rapper inspired by MF DOOM, and collaborates with other underrated rappers like gift of gab, and R.A.
big black guy with afro and glasses
Humphrey: Do you know A-F-R-O?
Jemsterjkan: no
Humphrey: cardi b sucks
Jemsterjkan: yes
by gauxapen March 22, 2021
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