1 definition by jalapeno101
An adjective used to describe someone who has no sense of self and is really out of place. "Mush Brain" is also used as a verb that means doing something stupid.
Adjective: Mikhail is so mush brain that he can't even speak with proper grammar.
Verb: Don't go full mush brain before watching anime!
Verb: Don't go full mush brain before watching anime!
by jalapeno101 July 8, 2021