Definition of unio
1 capitalized : the type genus of the family Unionidae comprising freshwater mussels that have an oblong shell pearly within and covered without by a greenish or blackish epidermis
2 plural unios \-ōz\ or unionides : any mussel of Unio or a related genus
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.
Start your free trial today and get unlimited access to America's largest dictionary, with:
- More than 250,000 words that aren't in our free dictionary
- Expanded definitions, etymologies, and usage notes
- Advanced search features
- Ad free!
Origin and Etymology of unio
New Latin, from Latin, a large pearl
Seen and Heard
What made you want to look up unio? Please tell us where you read or heard it (including the quote, if possible).