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Originally Posted by www.dictionary.com

fuck  /fʌk/ Pronunciation Key - Show Spelled Pronunciation[fuhk] Pronunciation Key - Show IPA Pronunciation Vulgar.

–verb (used with object) 1. to have sexual intercourse with.
2. Slang. to treat unfairly or harshly.
–verb (used without object) 3. to have sexual intercourse.
4. Slang. to meddle (usually fol. by around or with).
–interjection 5. Slang. (used to express anger, disgust, peremptory rejection, etc., often fol. by a pronoun, as you or it.)
–noun 6. an act of sexual intercourse.
7. a partner in sexual intercourse.
8. Slang. a person, esp. one who is annoying or contemptible.
9. the fuck, Slang. (used as an intensifier, esp. with WH-questions, to express annoyance, impatience, etc.)
—Verb phrases10. fuck around, Slang. a. to behave in a frivolous or meddlesome way.
b. to engage in promiscuous sex.

11. fuck off, Slang. a. to shirk one's duty; malinger.
b. go away: used as an exclamation of impatience.
c. to waste time.

12. fuck up, Slang. a. to bungle or botch; ruin.
b. to act stupidly or carelessly; cause trouble; mess up.

—Idiom13. give a fuck, Slang. to care; be concerned.

The context you used "Fuck off" in is slang, meaning not proper english. I think.