1. The head of a hammer.
2. 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.
3. 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.
4. An African fruit bat (Hypsignathus monstrosus), the male of which has a distinctive enlarged head.
(click for a larger image)hammerhead
scalloped hammerhead Sphyrna lewini
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.