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Acronym for "kick the f*ing ball." Literally, something you would yell during a game of soccer to someone who is staring at an open goal with no defender in sight.

However, in a more general sense, it means that someone is staring at a golden opportunity that can be easily achieved and all they need to do is to KTFB and get an easy win.
In soccer:
Announcer: Messi passes the ball to Milito inside the penalty box and Robert Green is off to get some fish n chips! KTFB!!

In life, generally:
Mr. A: That girl is totally hitting on me!
Mr. B: KTFB!!
by Siddy Boy July 21, 2010
Keep the fires burning. As in not forgetting an experience and keeping it close to heart. The phrase usually is referring to Camp Nebagamon.
Person A: "This was a great summer!!"

Person B: "I know! Remember to KTFB!!"
by Hammerguy4 September 25, 2011
kick the fuck back - when someone says something its its unbelievable
BoB: Dude, I totally banged that girl from last night.

Booby: KTFB
by Lor4 October 06, 2006
Knee Trembler From Behind
KTFB Figure it out for yourself dimwit
by Griptool September 14, 2007