Tête de bois (
teht duh bwah). This is the
all-purpose French
insult. It literally means "head of
wood", but can be used like the
English "
knuckle head", "
blockhead", "
numbskull",
etc.
Like most things in French, somebody is not a tête de bois, they 'have' a tête de bois. Here's how it is most often used:
Tu as un tête de bois = You're knucklehead!
Though slightly weak, it will get you respect/a punch in the face.