An acronym for Shut The Fuck Up. The illiterate mass that uses this seems to conveniently fail to realize that acronyms do not include a "T" for the article "the".
"If you ain't got nothing nice to say, then STFU."

"That's a double-negative."

"Huh, why do you speak in gibberish?"
by Killa Clownz November 6, 2008
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A phrase you use when you want someone to shut the fuck up.
Stfu, dammit. I don’t wanna hear your shit no more.
by TheRandomDoggo October 18, 2017
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The submission finishing move of John Cena. This hold is known in professional wrestling as the Stepover Toehold Sleeper (STS) and innovated by Masahiro Chono. The wrestler performs a stepover toehold and wraps his arm around the neck of the opponent as in a sleeper hold.
John Cena made Batista tap out when he applied the STFU.
by RGI May 14, 2007
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As of August 13th, 2009: International Suit Up Day.

STFU stands for "Suit the fuck up." It should be said when someone is not legendary (i.e not wearing a suit.) Should be said to anyone not wearing a suit on International Suit Up Day.
Person A (Wearing a suit) walks up to Person B (not wearing a suit)

Person A: "Dude STFU"
by Syko/Aran August 13, 2009
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Bill: STFU!

Jill: WHAT?!

Bill: *points to an angry unicorn* Shave it. It's furious
by MusicEmo June 14, 2010
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