Hammerhead

noun

1. The portion of a hammer containing the metal striking face (also including the claw or peen if so equipped).
2. Any of various sharks of the genus Sphyrna or Zygaena having the eyes set on projections from the sides of the head, which gives it a hammer shape.
3. A fresh-water fish; the stone-roller, in the minnow family Cyprinidae.
4. An African fruit bat, the hammer-headed fruit bat, Hypsignathus monstrosus, so called from its large blunt nozzle.
5. A stupid person, a dunce.