Acronym for 'Coming From Behind To Commence The Fucking'.

Vigorous, consenting, surprise sex from the rear.

Can also be used as an empty threat from one man to another.
“It’s me and Kelly’s 3 year anniversary tomorrow”
“what gift you getting her?”
“nothing, I was thinking of CFBTCTF like the good old days”

“don’t be a dick – if you keep this up I’m going to CFBTCTF”
by StupidPeanut April 23, 2010
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