A stupid person; it refers to the lack of surface area on an individual's brain. The general thought is that the more surface area (wrinkles, creases, etc.) a brain has, the smarter the person is. Conversely, a person with a smooth brain (no wrinkles) has less surface area and would therefore be stupid.
That fucking smooth brain put his shirt on backwards again...

That smooth brain is dumber than a pile of shit.
by Tip Tank May 14, 2011
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Opposite of big brain. Smooth brain refers to an idiot or someone dumb. Neuroscientists believe the more folds you have in your brain means the smarter you are. Therefore if you are called smooth brain, you have less folds and therefore dumb.
How did you forget to lock the door? Good move, smooth brain.

You don’t know basic math? Smooth brain 🙄
by TheoPham September 13, 2019
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adj. word to describe people that are slow or stupid

adj. describes unfunny, uncool people that are lame
“Oh look at Marquis, he’s so smooth brained
by dirtydikdan October 19, 2021
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Very smart person. their brain is smooth the is no resistance to knowledge
Brian has a smooth brain. Josh does not
by Brain Pretzel September 17, 2020
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When you underperformed at Magic the Gathering the most skill based game of all time so you convert to Flesh and Blood so you can win coin toss games.
I thought he was a smart guy so I avoided him cause i thought he was an incel but turns out he is a Smooth Brain Dickless Midget so i hooked up with him cause he is much easier to control.
by Vortakainia August 26, 2021
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An insult referring to the absence of wrinkles present in the human telencephalon(cerebrum) -- the largest region of the mammalian brain. Literally implying idiocy at a physiological level.
Those smooth-brained idiots voted for G.W. Bush twice!
by drastic_quench May 22, 2008
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A derogatory term used to describe someone after they have done something unintelligent, clumsy, or foolish. This term implies a below average intelligence due to an abnormally shaped brain. The expression is used almost exclusively for criticism.
Dude 1: Hey, did you hear that Mike literally got in an accident with a parked car yesterday!
Dude 2: Ya, I cant believe it. What an absolute smooth-brain.
by Mike N. Ike April 3, 2019
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