Definition of "hammerhead"

hammerhead

noun
plural hammerheads
1. The portion of a hammer containing the metal striking face (also including the claw or peen if so equipped).
2. (zoology) Any of various sharks of the genera Sphyrna or Zygaena having the eyes set on projections from the sides of the head, which gives it a hammer shape.
3. (zoology) A fresh-water fish; the hogsucker, Hypentelium nigricans, in the sucker family Catostomidae.
4. (zoology) An African fruit bat, the hammer-headed fruit bat, Hypsignathus monstrosus, so called from its large blunt nozzle.
5. (zoology) Scopus umbretta (hammerkop).
6. (slang) A stupid person, a dunce.
  Quotations
  [The butler] joined us with a telegram for Bobbie on a salver. From her mother, I presumed, calling me some name which she had forgotten to insert in previous communications. Or, of course, possibly expressing once more her conviction that I was a guffin, which, I thought, having had time to ponder over it, would be something in the nature of a bohunkus or a hammerhead.
  1960, P. G. Wodehouse, chapter V, in Jeeves in the Offing
7. A turn-around; a parking area constructed in a subdivision for initial access and construction.
8. (biology) A kind of ribozyme; hammerhead ribozyme.