A friend with which you occasionaly engage in sexual activity ranging from mutual masterbation to oral sex to intercourse. A true "FTF" relationship seldom involves kissing. If your kissing, its probably more than just a friend.
a.k.a. STF... Sinatra that fuck came from a Jerky Boys skit. Used to describe your unwillingness to listen to or the disappointment felt whilst hearing a Frank Sinatra song.
The wife and I ate at the Olive Garden last night. The food was good, but Jesus skydiving Christ the music sucks, they played Sinatra that fuck 4-5 songs in a row. Good food, shitty music!