ˈyünēˌō noun
Etymology: New Latin, from Latin, a large pearl — more at union III
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 uni·on·i·des ˌ ̷ ̷ ̷ ̷ˈänəˌdēz : any mussel of Unio or a related genus
• uni·oid ˈ ̷ ̷ ̷ ̷ˌȯid adjective