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Thought to have originated from the "That 70's Show" quote "...is that a thing?". Highschooler Joshua MacLatchie coined this phrase to mean you are absolutely sure that isn't even a real thing.

This also predates Seinfeld because fuck physics.
Ex:

Zach: I totally dunked my balls in her ass last night, shit was so cash.

Shim-sham: That's not even a thing.
by 100%RealFactChecker July 08, 2014
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