Someone who hasn't got a clue!
They live in blissful ignorance of the world, fashion, personal hygiene and social skills.

Invariably laughs like a baboon being repeatedly punched.

some one stupid.
from the word doof which is german for "stupid"

An foolish, incompetent or stupid person.

A total fucking idiot

A big, slow, dumbass

see also Homer Simpson

One who behaves in an irrational or immature manner

someone totally stupid, dumb and clueless (zong)