hammerhead

< /ˈhæm ərˌkɒp/. a brown heronlike African bird, Scopus umbretta, having the head so crested as to resemble a claw hammer.

Slang. blockhead; dunce; lout.

noun

any shark of the genus Sphyrna and family Sphyrnidae, having a flattened hammer-shaped head
a heavily built tropical African wading bird, Scopus umbretta, related to the herons, having a dark plumage and a long backward-pointing crest: family Scopidae, order Ciconiiformes
a large African fruit bat, Hypsignathus monstrosus, with a large square head and hammer-shaped muzzle

type of shark, 1843, from hammer (n.) + head (n.). So called for its broad, transverse head.