All brawn and no brains 

Idiom

Having great power or physical strength but lacking mental acuity or intelligence.

He may have been a good football player in high school, but he was all brawn and no brains, so he didn't get into any colleges.

All brawn and no brains by Zami Karzai September 1, 2018

nobrainlaina 

A term given to hateful and rude people by the Marauders fandom. Inspired by a user called nobrainlaina who used to love Jirius then became bitter and mean because James Potter (@JamesTheGreat) told her how bad her attitude was.

(THIS IS AN EXCERPT FROM THE WATTPAD BOOK “TALK SHIT” BY EVANAISSANTE

Person : she’s such a nobrainlaina!
-
Person : nobrainlaina is from a Wattpad book named Talk Shit.

nobrainlaina by wonderly June 15, 2018

no brains 

someone that has such a small brain that people think it doesn't exist

omg you have no brains

no brains by ededxde32wdsaxawere January 5, 2021

Balls No Brains 

Something you either need massive balls to do or zero brains.

Example with no brains

Bobby “Why is that guy riding a motorcycle with no helmet at 130 mile per hour (209 Kilometers per hour)?”
Brandon “That’s because he has a bad case of Balls No Brains”

Example with huge balls

Bobby “damn! That guy just punched one of the robbers in the face, too bad he’s about to get shot.”
Brandon “That guys got a serious Balls No Brains way of thinking.”

Balls No Brains by Closet Gayng October 21, 2021

Pre-mocks nobrain 

A serious mental condition, when IB students seem to lose all sense of the world around them. Can occur at any time before mock examinations and can last for looong periods. Also includes hysterical laughing or sudden sobbing.

"What are those students laughing at"
"They are laughing at a picture of Lenin holding Stalin as Virgin Mary does Jesus."
"...Why exactly?"
"I dunno. Probably pre-mocks nobrain."

Pre-mocks nobrain by Ayolandelena February 1, 2021