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noun. the inability to recall the simplest of details or solve the easiest of problems. a brain shit is much more serious than a Brain Fart.
guy #2: bro, you spelled cat wrong.

guy #1: wow. i just had a complete brain shit.
by Brent Handles November 24, 2009
this is bullshit, which consistently comes from a certain person.
That kieron kid constantly brainshits
by TheChrissy09 March 15, 2009
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?!
by Jjjjjjjjjjjjjjjj September 08, 2005