[n] medium-sized live-bearing shark with eyes at either end of a flattened hammer-shaped head; worldwide in warm waters; can be dangerous [n] the striking part of a hammer [n] these words are used to express a low opinion of someone's intelligence
blockhead, bonehead, dunce, dunderhead, fuckhead, hammerhead shark, knucklehead, loggerhead, lunkhead, muttonhead, numskull, shithead