A brain genius is what you get when you cross a rocket scientist and a brain surgeon. Can be used sarcastically, or as an actual compliment.
Guy 1: We should jump off the roof!

Guy 2: Yeah... great idea brain genius.

Guy 1: No, we don't have to buy a new one, we can just duct tape it.

Guy 2: I didn't even think of that! You're a brain genius!
by AGun June 17, 2010
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To be a smart ass

Also Youtuber DavidSo's podcast
Genius Brain is Always using sarcasm, stating the obvious, etc.
by Acelus April 14, 2019
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you're dumb but you do something smart for once
that dude over there is a small brain genius, he accidentally poured some substance into whatever tf that is and created it into a new material.he is getting the nobel peace prize rn
by RadicalMuffin December 6, 2020
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