Jeffy is a term used, mostly in Ontario, to describe one who's actions have left no doubt in everyone, that he is a moron and/or just a Tard.

Do not mistake with the Name of an individual.
X: Sorry man, I spilt my beer on your bed...
Y: You Jeffy!
Crowd: JEFFY!!!
by Groscave December 1, 2010
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A puppet, named by Logan Thirtyacre, otherwise known by his YouTube channel name SuperMarioLogan.

Jeffy hates green beans, sticks pencils in his nose and he beats his diaper. He’s a mentally challenged child who wears a bicycle helmet everywhere.
Jeffy: F YOU DADDY!

Mario (Jeffy’s dad): Jeffy don’t say that!
by 🧀 March 10, 2018
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Originated as a colloquialism long long ago, reaffirmed and popularized through references such as the movie Corker with Johhny Knoxville, 'Jeffy' is a literal substitution for retarded.
I need you to buy me a trenchcoat while you are in Russia. In regards to style, you have keen eye for stuff that doesn't look Jeffy right?
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What? You want me to work on my wedding day?! That's absolutely fucking Jeffy, dude.
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Psst, listen to what I call that kid with Down's Syndrome over there.
"Hey Jeffy!"
He just smiled at me...
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Man, you gotta quit drinking; you're acting Jeffy and I'm gonna kick your ass if you keep it up.
by BioMenace November 12, 2006
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Jeffy is a very sexy puppet with nice fashion sense with clothing saying

"Jeffy" and having a hand up his butthole. Jeffy likes to become a robot for no apparent reason and shoot laser beams at his father Mario. He also may have anger issues and slight bipolar problems because of the fact that his now dead father fed him green beans everyday for every meal. One day after inhaling his Skecher fumes he suddenly raged and killed his beloved Mario green bean lover. Jeffy is now kidnapped and being raped by Aretta (Thunderthigh29's ex)
I heard Jeffy the hawt bad boy of the school killed his loving green bean loving father Mario!
by Arinterstellar January 14, 2018
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An autistic puppet how spanks his diaper and and abuses his Cheerio boxes. He is also the best rapper in the game.
Yo Jeffy is in jail for annaly raping a cheerio box nigga.
by Jgrande22 May 30, 2019
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jeffy is a very green-been hating, cheerio raping puppet who hates green beans
jeffy: daddy can i go smack my peepee
by Yee OOF September 3, 2018
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