Braincest 

In certain circumstances, two children will be born, sometimes even from different parents, and they will be siamese. However, not siamese physically, but mentally. If such children with siamese brains partake in any physical activities, it is called braincest.

Kathy and Jake are getting married? That's braincest!

Braincest by Josh Osborn May 23, 2008

brainlet

immature,underdeveloped cerebral cortex,unfit for real world survival

Jimmy scored ninety on the I.Q.test. What a brainlet!

brainlet by TinFoilHatGuy May 11, 2017

Brainlet

Someone associated with having a low iq and a below average common sense.

Tilly you brainlet!

Brainlet by Kaprie May 30, 2018

Brainlet

Individuals that search their names on Urban Dictionary and share the definition with others in order to feel good about them seleves. These people generally have IQs equivalent to that of small fish and think that Lelepons is funny.

"Hey, check out that brainlet over there."

Brainlet by go commit neck rope July 12, 2018

brainrection

A condition that exists when all of the blood rushes to your brain. Typically brought on by shocking, interesting, or new information.

I had a full-on brainrection, when I heard the news about Thomas Coyne.
That movie was a Total brainrection.
After reading that book I couldn't get a brainrection for a month.

brainrection by DerelictDoug.net June 18, 2020

Bincest 

The act of putting two bins from the same house on top of each other. Essentially incest but with bins.

Those bins are stacked on top of each other.
Yeah they're having bincest.

Bincest by OctagonDinosaur September 19, 2016

Brainless

A person that acts without any care of what'll be the consequences of what he's doing. Also a stupid, superficial, dull person.

1. Oh, damn! You act like you're brainless! Don't you think about what will happen if you do that?

2. That boy's brainless. I suggest you to not go out with him.

Brainless by KD Squib September 10, 2005