Definition of Hydractinia
: a genus of marine hydroids that have separate and distinctive polyps for nutritive, reproductive, and defensive functions borne on a dense encrusting coenosarc and that are commonly associated with shells containing hermit crabs
hydractinianadjective or noun
Love words? You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.
Join MWU now and get access to America’s largest dictionary, with:
- 300,000 words that aren't in our free dictionary
- Expanded definitions, etymologies, and usage notes
- Advanced search features
- Ad free!
Origin and Etymology of hydractinia
New Latin, from hydr- + Actinia
Seen and Heard
What made you want to look up Hydractinia? Please tell us where you read or heard it (including the quote, if possible).