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1. A random word stem collected from a popular internet word (ie, post) and utilized by internet spam bots to form a new word. Common affixes include one to four length letters, or a jumble of letters, used in an attempt to cover as many unique combinations as possible to drive traffic to their websites.

2. A frequent typo, randomly typed letters, or misspelling by internet users.

3. Common abbreviation for "Please Only Save The Friendly Unicorns", an organization dedicated to the preservation of friendly unicorns located in the Canadian wilderness.

4. Common abbreviation for "Pictures Or Shut The F* Up", a definition conceived by a single individual but not actually common or used at all. Unless you count that one time ten years ago.

5. Or, this word could mean absolutely nothing at all and it's just a completely random word created with no real meaning or common use in the real world or the internet, and anyone can choose how they want to define the word. This is just an example of how easy it is to submit a definition and have it accepted by editors who approve almost anything based entirely on how funny it is and if the definition contains no spelling errors.
"C'mon, POSTFU."
"Hey man! POSTFU."
"Oh no, it's POSTFU."
by Symguy June 23, 2013
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1. "Pics Or Shut The F*ck Up". Used on message boards to mean that the author is talking about something that requires visual evidence that should either be produced or the matter should be dropped.
"I met this hot chick over at the bar last night."
"C'mon, POSTFU."
by Raiderpower September 12, 2006
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