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.