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1.
That Shit Is Fucked
Guy 1 : Gawd Damn this is some good ass ice cream.
Guy 2 : Let me get a lick of that shit dawg.
Guy 1 : TSIF
Guy 2 : Come on, you know I'm straight busted till the furst of da Month.
by monkeydance February 19, 2009
 
2.
Meaning "Thank Satan It's Friday"

Similar to "TGIF", but used by Satanists.
TSIF! I'm going to drink some pig blood.
by Bloodbath87 March 04, 2009