an expression; usually directed towards a particularly stupid guy who wants to do something inappropriate to you.
however dont expect them to understand this simple phrase when you say it. they'll act confused and be all like what?
just warning you.

Prehaps one of the most interesting words
In the English language today is the word fuck
Out of all the English words that begin with the letter "f"
Fuck is the only word that is referred to as the "f"word
It's the one magical word
Just by it's sound can describe pain, pleasure, hate and love
Fuck, as most words in the English language, is derived for German
the word "fleckin" which means to strike
In English fuck falls into many grammatical categories
As a transitive verb for instance
"John fucked Shirley."
As an intransitive verb
"Shirley fucks."
It's meanings not always sexual
It can be used as an adjective as in
"John's doing all the fucking work."
As an adverb
"Shirley talks too fucking much."
As an adverb enhancing an adjective
"Shirley is fucking beautiful!"
As a noun
"I don't give a fuck!"
As a part of a word
"Absofuckinglutly!"
or
"Infuckincredible!"
And as almost every word in the sentence
"Fuck the fucking fuckers."
But you must realize that aren't too many words
With the versatility of fuck
As in these examples describing situations such as
Fraud
"I got fucked at the used car lot."
Dismay
"Ah fuck it!"
Trouble
"I guess I'm really fucked now."
Aggression
"Don't fuck with me buddy"
Difficulty
"I don't understand this fucking question"
Inquiry
"Who the fuck was that?"
Disatisfaction
"I don't like what the fuck is going on here."
Incompetantce
"He's a fuck off"
Dismissal
"What don't you go outside and play hide-a...

When a man sticks his erect penis in a womans wet vagina and his friend spins him around.

When you drive your huge hard cock into your girlfriend's pussy, to give her the "big o" with your big one.
There are a number of slang terms for fuck. Among the most common are sex, sexual intercourse, make love, and go all the way.

A roundabout way of saying "go fuck yourself."

"Fuck" is perhaps the most versatile and most-used word in the English language. It can relate anger, surprise, dismay, joy, and a variety of other emotions. It is also quite commonly used as a word of emphasis or description, often with comical effect. For some good examples, refer to "English as a Second Fucking Language," by Sterling Johnson, which can be found on Amazon.com. Also check out comic Dane Cook's take on the word.

Also, on a rather interesting note, I read somewhere that fucking once described an act in which a person who sowed/planted seeds in a field, and those particular people were referred to as fuckers.

NOTE:

The guy who quoted Monty Python had it wrong. I believe the quoted text is attributed to George Carlin.

Commonly said when you are at the end of your rope doing anything at all. Normally after you have felt bitchy and pissed off all day.