- the head of a hammer, specif. the part with a flat surface for striking
- any of a family (Sphyrnidae, order Carcharhiniformes) of large, tropical sharks that have a mallet-shaped head with an eye near the center of each end
- a very large African fruit bat (Hypsignathus monstrosus) with a large horselike head
- a large, brownish, crested African wading bird (Scopus umbretta) of a family (Scopidae) with only one species
- The head of a hammer.
- Any of several predatory sharks of the genus Sphyrna, having the sides of the head elongated into fleshy extensions with the eyes at the ends.
- A wading bird (Scopus umbretta) of Africa and Arabia, having brown plumage, a large bladelike bill, and a long backward-pointing crest. Also called hamerkop.
- An African fruit bat (Hypsignathus monstrosus), the male of which has a distinctive enlarged head.
scalloped hammerhead Sphyrna lewini
- The portion of a hammer containing the metal striking face (also including the claw or peen if so equipped).
- (zoology) 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.
- (zoology) A fresh-water fish; the stone-roller, in the minnow family Cyprinidae.
- (zoology) An African fruit bat, the hammer-headed fruit bat, Hypsignathus monstrosus, so called from its large blunt nozzle.
- (slang) A stupid person, a dunce.
- (biology) A kind of ribozyme; hammerhead ribozyme.