hammerhead

(noun) a stupid person; these words are used to express a low opinion of someone's intelligence. Synonyms: dunce, dunderhead, numskull, blockhead, bonehead, lunkhead, knucklehead, loggerhead, muttonhead, shithead, dumbass, fuckhead.

(noun) the striking part of a hammer.

(noun) medium-sized live-bearing shark with eyes at either end of a flattened hammer-shaped head; worldwide in warm waters; can be dangerous. Synonyms: hammerhead shark.