We found 28 dictionaries that define the word harmful:

General (24 matching dictionaries)

1. harmful: Merriam-Webster.com
2. harmful: Oxford Learner's Dictionaries
3. harmful: American Heritage Dictionary of the English Language
4. harmful: Collins English Dictionary
5. harmful: Vocabulary.com
6. Harmful, harmful: Wordnik
7. harmful: Cambridge Advanced Learner's Dictionary
8. harmful: Wiktionary
9. harmful: Webster's New World College Dictionary, 4th Ed.
10. harmful: The Wordsmyth English Dictionary-Thesaurus
11. harmful: Infoplease Dictionary
12. harmful: Dictionary.com
13. harmful: Cambridge Essential American English Dictionary
14. Harmful: Wikipedia, the Free Encyclopedia
15. Harmful: Online Plain Text English Dictionary
16. harmful: Webster's Revised Unabridged, 1913 Edition
17. harmful: Rhymezone
18. harmful: AllWords.com Multi-Lingual Dictionary
19. harmful: Webster's 1828 Dictionary
20. harmful: Free Dictionary
21. harmful: Mnemonic Dictionary
22. harmful: Dictionary/thesaurus

Business (2 matching dictionaries)

23. Glossary of Legal Terms (No longer online)
24. harmful: Legal dictionary

Science (1 matching dictionary)

25. Harmful: HYPP Zoology

Tech (1 matching dictionary)

26. AUTOMOTIVE TERMS (No longer online)

(Note: See harmfully as well.)

Definitions from Wiktionary ( ) ▸ adjective:  Causing or likely to cause harm or damage; injurious. Similar: detrimental, injurious, damaging, hurtful, pernicious, noxious, pestilent, deleterious, insidious, baneful, more... Opposite: beneficial, harmless, safe, helpful, advantageous Types: carcinogenic, toxic, radioactive, corrosive, flammable, explosive, more... Phrases: Considered harmful, medicine that is harmful and ineffective, Harmful algal bloom, Harmful If Swallowed, Federal Department for Media Harmful to Young Persons, more... Adjectives: harmless, noxious, irritant, less, toxic, much Colors:     black,     red,     dark gray,     neon green,     brown, more... ▸ Words similar to harmful ▸ Usage examples for harmful ▸ Idioms related to harmful ▸ Wikipedia articles (New!) ▸ Popular nouns described by harmful ▸ Words that often appear near harmful ▸ Rhymes of harmful ▸ Invented words related to harmful