n. pl. nem·e·ses (-sēz′)
1. A source of harm or ruin: Uncritical trust is my nemesis.
2. Retributive justice in its execution or outcome: To follow the proposed course of action is to invite nemesis.
3. An opponent that cannot be beaten or overcome.
4. One that inflicts retribution or vengeance.
5. Nemesis Greek Mythology The goddess of retributive justice or vengeance.
[Greek, retribution, the goddess Nemesis, from nemein, to allot; see nem- 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.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.