Merriam-Webster Logo
SINCE 1828
Menu
×

An Encyclopædia Britannica Company

See What's Trending Now See More Trending Words

unio

noun \ ˈyünēˌō \

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
—

unioid

adjective

People Are Reading

image536372841
Every Letter Is Silent, Sometimes
alt-59c2960017c94
The Ambiguity of Pushing 'Up' and 'Back'
alt-59c2cb9e9ef54
Trending: Ivanka: "An 'Otherwise' Incredible Day"
video-title-words-of-the-year-1066
Words of the Year: 1066

There's more!

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!
Already a subscriber? Log in.

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).

show hide

Love words? Need even more definitions?

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

WORD OF THE DAY

holus-bolus

play

all at once

Get Word of the Day daily email!

TRENDING NOW

  1. otherwise "in other respects"

  2. federalism Graham says bill gives power to states

  3. bodega "Don’t mess with the beloved bodega."

  4. carceral Of, relating to, or suggesting a jail or prison

  5. allegory No spoilers!

SEE ALL

Love words? Need even more definitions?

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

Words at Play

alt-59c2960017c94
The Ambiguity of Pushing 'Up' and 'Back'

When you push a meeting, where does it go?

image536372841
Silent Letters

When each letter can be seen but not heard

alt-59c17b8172892
'So Long': A Common But Mysterious Goodbye

Its origins are surprisingly murky.

alt-59c13729150dc
"Immune to" or "Immune from"?

Nobody is immune to this question.

Ask the Editors

video-title-words-of-the-year-1066
Words of the Year: 1066

Or, Why Pig Meat is Called 'Pork' and Cow Meat is Called 'Beef'

payday
How Often Is 'Biweekly'?

Don't get us started on 'bimonthly'

video-irregardless-grammar-peeve-blend-of-the-synonyms-irrespective-and-regardless
Irregardless

It is in fact a real word (but that doesn't mean you should use it).

video-moose-goose-weird-plurals
Weird Plurals

One goose, two geese. One moose, two... moose. What's up with that?

Word Games

young-plant-shoots
Merriam-Webster's New Words Quiz—Fall 2017 Edition!

You're going to have to memorize the dictionary again.

Take the quiz
stylized-drawing-of-woman-pole-vaulting-across-gap-to-get-trophy
Challenging Vocabulary Quiz Returns!

No tricks, just difficult words.

Take the quiz
Spell It
Spell It

Can you spell these 10 commonly misspelled words?

Take the quiz
Citation
Citation

Do you know the person or title these quotes describe?

Play the game