a. A protective head covering made of hard material, such as leather, metal, or plastic: A firefighter's uniform includes a helmet.
b. The headgear with a glass mask worn by deep-sea divers.
c. A pith helmet; a topi.
d. A head covering, such as a balaclava, that is shaped like a helmet.
2. A piece of armor, usually made of metal, designed to protect the head.
3. Botany The hood-shaped sepal or corolla of some flowers.
tr. & intr.v. hel·met·ed, hel·met·ing, hel·mets
To provide with or put on a helmet.
[Middle English, from Old French, diminutive of helme, of Germanic origin; see kel-1 in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 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.