A Mench
A Mench is a brainiac who thinks they're the smartest person in the room. They talk like they just graduated from genius school.
My math teacher is a Mench. He once solved a problem that took me three hours in, like, ten seconds.
My cousin is a Mench. She can name every planet in the solar system and still beat me at chess.
My neighbor is a Mench. He reads books while eating pizza and still has time to text me insults.