American chat english for "This Is So Not Fair".
Usually used when parents take away cell phones due to severly high phone bills.
(Yeah this is from the commercial)
Mom: Well I'm taking away your cell phone Girl: TISNF!!!
Mom: I'll tell you...what's...SNF...
TISNF has become the icon for preppy girls that never seem to stop texting, or have a valleygirl accent. TISNF stands for "this is so not fair" and is taken from a cell phone commercial campaign by cingular, now AT & T. used to imitate women in a sarcastic manner, usually when they flip out about something that's really not that big a deal, throw in a TISNF to get a laugh out of the guys listening.
That is so not fair! One of many acronyms that have been created by the IM age (instant messaging) that we live in.
q.v. NBD (no big deal) and BFF (best friends forever).
TISNF, Mom | Dad (When confining kid to bedroom or preventing him from playing a computer game, for example).