We found 24 dictionaries that define the word hydroid:

General (19 matching dictionaries)

1. hydroid: Merriam-Webster
2. hydroid: Oxford Learner's Dictionaries
3. hydroid: American Heritage Dictionary of the English Language
4. hydroid: Collins English Dictionary
5. hydroid: Vocabulary.com
6. Hydroid, hydroid: Wordnik
7. hydroid: Wiktionary
8. hydroid: Webster's New World College Dictionary, 4th Ed.
9. hydroid: The Wordsmyth English Dictionary-Thesaurus
10. hydroid: Infoplease Dictionary
11. hydroid: Dictionary.com
12. Hydroid (botany), Hydroid (zoology), Hydroid: Wikipedia, the Free Encyclopedia
13. Hydroid: Online Plain Text English Dictionary
14. hydroid: Webster's Revised Unabridged, 1913 Edition
15. hydroid: Rhymezone
16. Hydroid: AllWords.com Multi-Lingual Dictionary
17. hydroid: FreeDictionary.org
18. hydroid: Mnemonic Dictionary
19. hydroid: TheFreeDictionary.com

Computing (1 matching dictionary)

20. hydroid: Encyclopedia

Medicine (3 matching dictionaries)

21. hydroid: Merriam-Webster Medical Dictionary
22. online medical dictionary (No longer online)
23. hydroid: Medical dictionary

Science (1 matching dictionary)

24. Bryological (No longer online)

(Note: See hydroids as well.)

Definitions from Wiktionary (hydroid) ▸ noun:  Any of many colonial coelenterates that exist mainly as a polyp; a hydrozoan ▸ adjective:  Of or pertaining to such creatures Similar: hydrozoan, hydropolyp, hydranth, polyp, gastrozooid, polypifer, polypite, hydrosome, hydrophyton, polypiarian, more... Phrases: hydroid polyps, hydroid polyp, more... Adjectives: colonial, marine, small, branched, new, asexual, tubularian, stinging, typical, certain, commensal ▸ Words similar to hydroid ▸ Usage examples for hydroid ▸ Idioms related to hydroid ▸ Wikipedia articles (New!) ▸ Popular adjectives describing hydroid ▸ Popular nouns described by hydroid ▸ Words that often appear near hydroid ▸ Rhymes of hydroid ▸ Invented words related to hydroid