The DICT Development Group

  Hammerhead \Ham"mer*head`\ (-h[e^]d`), n.
     1. (Zool.) A shark of the genus Sphyrna or Zyg[ae]na,
        having the eyes set on projections from the sides of the
        head, which gives it a hammer shape. The Sphyrna
        zyg[ae]na is found in the North Atlantic. Called also
        hammer fish, and balance fish.
        [1913 Webster]
  
     2. (Zool.) A fresh-water fish; the stone-roller.
        [1913 Webster]
  
     3. (Zool.) An African fruit bat ({Hypsignathus monstrosus);
        -- so called from its large blunt nozzle.
        [1913 Webster]

  hammerhead
      n 1: a stupid person; these words are used to express a low
           opinion of someone's intelligence [syn: dunce,
           dunderhead, numskull, blockhead, bonehead,
           lunkhead, hammerhead, knucklehead, loggerhead,
           muttonhead, shithead, dumbass, fuckhead]
      2: the striking part of a hammer
      3: medium-sized live-bearing shark with eyes at either end of a
         flattened hammer-shaped head; worldwide in warm waters; can
         be dangerous [syn: hammerhead, hammerhead shark]