ˌ ̷ ̷ ̷ ̷ˈänəˌdē noun plural
Usage: capitalized
Etymology: New Latin, from Union-, Unio, type genus + -idae
: a very large family of freshwater mussels (suborder Submytilacea) having a pearly often roughly sculptured shell with a thick epidermis and larvae that pass through a glochidium stage and being represented in nearly all parts of the world but chiefly in No. America where the nacreous shells of many of them are used for button making