n. pl. no-noes
1. Something unacceptable or impermissible: "Even though his company wasn't the one involved in the case, what he did is considered a definite no-no" (Mike Royko).
2. A social blunder; a faux pas.
3. Baseball A game in which a pitcher allows no hits and no runs.
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.