Synonyms for Bozo:

n.

lump, maniac, airhead, joker, fool, numpty, dumb blond. bozo (noun)
fathead, cuckoo, goose, cat, goof, hombre, guy, zany, twat.
buffoon (noun)
joker, zany, fool.
person (noun)
cuckoo, goose, goof, fathead, zany, twat.
screwball (noun)
goof.

Other synonyms:

n.
fool, zany.