ad·a·man·tine (ăd′ə-măntēn′, -tīn′, -tĭn)
1. Made of or resembling adamant.
2. Having the hardness or luster of a diamond.
3. Unyielding; inflexible: "If there is one dominant trait that emerges from this account, it is adamantine willpower" (Eugene Linden).
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 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.