gabshite
A gabshite is a person who acts like they're the king of the castle, doing dumb stuff just to look cool and not caring if people laugh at them.
My brother is a gabshite. He ran into the grocery store wearing only socks and a hat.
My friend is a gabshite. She tried to sing a whole song in the middle of the hallway and failed.
My dog is a gabshite. He ate my homework and then barked at my math teacher.