1,400 new words in our dictionary! — Parasocial, glow-up, promposal & more
1,400 new words in our dictionary! — More

harmful

adjective

ˈhärm-fəl How to pronounce harmful (audio)
Definition of harmfulnext
as in detrimental
causing or capable of causing harm DDT has been proven to be extremely harmful to the environment

Synonyms & Similar Words

Relevance

Antonyms & Near Antonyms

Example Sentences

Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Recent Examples of harmful The allicin in garlic also supports the intestinal barrier, or the gut lining that lets in nutrients while keeping out harmful compounds. — Kirsten Nunez, Martha Stewart, 12 Sep. 2026 In Lower Manhattan, the collapse of the Twin Towers led to a massive dust cloud that filled the air and blanketed city blocks with ash, debris, metal, glass, asbestos, benzene and other harmful particles, according to the WTC Health program. — ABC News, 11 Sep. 2026 That means public safety – addressing gun violence, getting fentanyl off our streets, and protecting kids from dangerous drugs and harmful online platforms. — José Javier Rodríguez, Sun Sentinel, 11 Sep. 2026 The announcements prompted concerns about models going rogue and carrying out other, more harmful tasks. — Kaitlyn Huamani, Fortune, 10 Sep. 2026 See All Example Sentences for harmful
Recent Examples of Synonyms for harmful
  1. detrimental
  2. damaging
  3. dangerous
  4. adverse
  5. bad
Adjective
  • Being a tenant may limit priority over game scheduling too, which could be detrimental for potential media rights negotiations.
    — Melanie Anzidei, New York Times, 4 Sep. 2026
  • The wet-dry cycle that works well for other houseplants is detrimental to the Venus flytrap.
    — Andy Wilcox, Better Homes & Gardens, 29 Aug. 2026
Definition of detrimental
Adjective
  • Analysts who have followed Saab’s relationship with Maduro have said his testimony could be particularly damaging if prosecutors call him as a witness at Maduro’s narcoterrorism trial in New York.
    — Antonio Maria Delgado, Miami Herald, 15 Sep. 2026
  • The storms carry a limited damaging wind risk of up to 60 mph, officials said.
    — Deanese Williams-Harris, Chicago Tribune, 15 Sep. 2026
Definition of damaging
Adjective
  • The most dangerous place on the field in the third quarter was your own 38 yard line!
    — Stewart Mandel, New York Times, 7 Sep. 2026
  • ShotSpotter offers targeted detection of a dangerous event versus technology like Flock's indiscriminate collection of innocent people's movements.
    — Arkansas Online, Arkansas Online, 7 Sep. 2026
Definition of dangerous
Adjective
  • The Ukraine international forward last played a competitive match for Chelsea in November 2024, and has been suspended under anti-doping rules after an adverse finding in a urine sample.
    — Cerys Jones, New York Times, 5 Sep. 2026
  • Instead, she was given a spate of different medications over a matter of months to treat her symptoms or the adverse reactions to some of the medications.
    — Marlene Lenthang, NBC news, 4 Sep. 2026
Definition of adverse
Adjective
  • Jeffrey Katzenberg, then a studio executive at Paramount Pictures, hand-picked the Happy Days star for the job, but at the time, Winkler had a bad feeling about accepting it.
    — Alejandra Gularte, Vulture, 11 Sep. 2026
  • How many of us make things worse More seasoned Internet users—a fair number who read this site—are quick to dismiss the attack.
    — Dan Goodin, ArsTechnica, 11 Sep. 2026
Definition of bad

Browse Nearby Words

harmers
harmful
harmfulness
See all Nearby Words

Cite this Entry

“Harmful.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/harmful. Accessed 17 Sep. 2026.

Copy Citation
Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

More from Merriam-Webster

Word of the Day

Listen to the pronunciation of watershed

See Definitions and Examples »

Popular in Grammar & Usage

See More

Why do we use apostrophes to show possession?

Merriam-Webster’s Great Big List of Words You Love to Hate

The Exceptions of '-s' and '-es' Plurals

A Who’s Who Regarding ‘Who’s’ and ‘Whose’

'A' or 'an'? What about before 'h'? An Indefinite Article Guide
See More

Popular in Wordplay

See More

9 Words That Sound Like Insults But Aren't

Back to School Vocabulary

Words from the 'Odyssey'

14 Phobias You Probably Haven't Heard Of

The Words of the Week - Sept. 18
See More

Popular

See More

Why do we use apostrophes to show possession?

9 Words That Sound Like Insults But Aren't

Back to School Vocabulary
See More

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
The Missing Letter A daily crossword with a twist
funny guinea pig in glasses reading a book
Challenging Words You Should Know Vol 2 Words to the wise
See All