daft dildo
A person who's not just dumb, but also thinks they're the smartest person in the room. Like a dead fish that still thinks it's swimming.
He said he could solve the universe with a ruler. You said, 'You’re a daft dildo.'
He tried to explain the moon with a banana. You called him a daft dildo.
He thought he was famous. You said, 'You’re a daft dildo.'