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1.
Fuck You If You Disagree *

a) To "gently" persuade someone that your opinion matters more than theirs. Which of course it does.

b) A way to end a futile attempt to lift the awareness of the obviously ill-informed person with whom you're interacting (e.g., an asshat, buttmunch, fucktard, or similar).

c) STFU

* Usually used online during intellectual discourse, but rare instances have been discovered in letters involving spats between romantic partners (see white trash).
(we join the following conversation already in progress)

aaron: STFU! my gf's hot, and all y'alls moms are ugly, skanky hoes. FUIUD!!
fred: yer mom ain't winnin any prizes either, dude
don: hang on - yo, take that out of your mouth and look up at me. I'll have to disagree - except for the lazy eye, aaron's mom is bangin' ...
fred: lol
nerf: lol
aaron: fuck off
by MechaRobzilla April 19, 2011
 
2.
Acronym for "Fuck you if you disagree."
Lazer tag is awesome, FUIUD.
by VincentJC April 14, 2011