in Mathematics and Physics IFF stands for " if and only if ".
For P(x), IFF P(a)=0, then (x-a) is a factor of P(x).
by arysmart May 19, 2013
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An organization know as the I'm Fucked Foundation.
Ronnie Magro is currently president, CEO, and founder of this establishment by stuffing his face in a cocktail waitress' tits and then making out with two other chicks.
I joined the IFF today by fucking my best friend's sister.
by icedemon25 September 3, 2010
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This is the IM FUCKED FOUNDATION. you join this club when nothing goes your way or you feel as though the world is ganging up on you
i just told my girlfriend i cheated on her, i just became apart of the IFF.
by ARAE1989 August 7, 2010
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Identification: Friend or Foe. A system used by the military to distinguish between friendlies and hostiles.
The IFF tagged the aircraft as friendly.
by Ben Roberts May 12, 2005
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I put on a rainbow dress and glitter eyeshadow today, IFF
by jesslynn666 March 30, 2013
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Inappropriate Facebook Friend- In which two people are Facebook friends with one another despite the fact that is completely inappropriate.
Often found in cases when adult males send friend requests to the high school or college aged children of their coworkers or friends.
Also common when someone is sexually attracted to but is unwilling or unable to pursue an actual relationship with a person; and thus substitutes Facebook friends status in order to be involved, even peripherally, with the person of interest.
When the inappropriate nature of the friend status is recognized by both people, IFF status enables them to view each others photos and send messages to one another without actually having to explain the contact to those who might disapprove of the interaction.
James has a niece attending college nearby, and she friended him on facebook. Since then, he has become IFF's with dozens of her female classmates. This enables him access to their photos, which he enjoys quite a bit.

Clarice and her son's lacrosse coach find each other incredibly attractive. They both look forward to every match when they can see each other. Since actual social interaction would be potentially damaging to both of them, they are content to be IFF's, occasionally sending innuendo-filled messages or swapping photos.
by Sailor Mike June 23, 2011
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