To literally shit using your brain instead of your (or another's) anus. Most often done by people who want to make up definitions to words that don't really exist in order to appear in an online "definitions" database.
Most people posting things to "The Urban Dictionary" are just taking huge brainshits.
Hey Cody! Earl, Jordan and me just posted a definition of "ba-donk-a-dank". Of course, "ba-donka-donk" was already done, but we just wanted to brainshit. Aren't we cool?!
Branchshitty is a poor teacher at Brentsville District High School who hates every student who’s opinion differs from his own. He fails students regularly because he doesn’t agree with them.
Man, did you get Branshitty?
Branshitty failed me because I don’t agree with his opinions.
When finance content creators rent out fancy cars and flexcash to seem richer than they really are in order to promote and sell their “get rich quick” courses.
The use of the word "blue" to refer to sexually explicit content was first recorded in Scotland in 1824. "Blue" meant "lewd" because prostitutes dressed in blue gowns.