1. Offensive to the point of arousing disgust; foul: a noisome odor.
2. Harmful or dangerous: noisome fumes.
[Middle English noiesom : noie, harm (short for anoi, annoyance, from Old French, from anoier, to annoy; see ANNOY) + -som, adj. suff.; see –SOME1.]
Usage Note: People sometimes assume that noisome means "noisy," because the two words sound similar. But in our 2011 survey, 89% of the Usage Panel found the sentence We could barely hear each other with the noisome helicopter overhead to be unacceptable. If you use noisome as a synonym for noisy, there's a good chance that others will misinterpret your words and think you're describing someone or something as being offensive or harmful.
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.