Ham·mer·head n.
 1. Zool. A shark of the genus Sphyrna or Zygaena, having the eyes set on projections from the sides of the head, which gives it a hammer shape. The Sphyrna zygaena is found in the North Atlantic. Called also hammer fish, and balance fish.
 2. Zool. A fresh-water fish; the stone-roller.
 3. Zool. An African fruit bat (Hypsignathus monstrosus); -- so called from its large blunt nozzle.
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