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 15, 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 14, 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 20, 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 18, 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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A brain that has the quality of smoothness: having an even and consistent surface
Person 1: Wow! Person 2, I am feeling your exposed brain right now, it is so smooth and without wrinkles or blemish. Such a smooth brain!
Person 2: Thank you, Person 1, your compliment is received in a sense of nuanced gratification. I can only imagine the physical ramifications of the immense, sweltering envy you possess as a result of the sheer superiority I display before you, both corporeal and cognitively.

Person 1: Ok, jackass.
by Phil Johnson 47 December 5, 2020
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J: O, you have a smooth brain
O: Does this mean I have a cute brain?
*L, M, N, O, and P all start laughing*
by Ace the simp May 6, 2023
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