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1.
Come The Fuck In, opposite of Get The Fuck Out. Usually used after being told 'Tits or GTFO' previously.
Guy 1: Tits or GTFO
Guy 2: Dude, I just got pics of her tits last night, can i CTFI now?
by maynor May 01, 2011
 
2.
Cum The Fuck In -
It is usually used by the female role in sexual intercourse, but sometimes may be treated as the polar opposite of G.T.F.O.
Man: You'd better let go, baby! I'm about to cum.
Woman: C.T.F.I., Baby!
Man: What? I don't u....uaaAAAGH!
by Huahahahaha March 30, 2011