tr.v. un·der·mined, un·der·min·ing, un·der·mines
1. To weaken by wearing away a base or foundation: Water has undermined the stone foundations.
2. To weaken, injure, or impair, often by degrees or imperceptibly; sap: Late hours can undermine one's health.
3. To dig a mine or tunnel beneath.
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.