Literally a contraction of 'fuck off no thanks'. When used literally, it denotes a loathing and sarcastic 'no thanks'. However it is frequently used without rancour to denote the canceling of a social engagement.
2. When asked to do something horrendous at work - "Oh, fonx."
1). a noun meaning "a very very very fit person, who you'd shag RIGHT now."
2). a verb meaning whatever you want it to mean. you can fonx a person, a play, a piece of homework, anything.
3). an exclamation of self admiration, following an amazing action, a witty remark, etc.
*looking at lady...* "fonx"
"i totally fonxed that exam."
"i wanna fonx you, you fonx"
"come fonx with me, let's fonx, let's fonx away"
*having just pwned a driving test* "FONX!"
"Fonx; i pwned you."