the GNU version of the Collaborative International Dictionary of English
n. Any one of numerous species of fresh-water mussels belonging to Unio and many allied genera.
The Century Dictionary and Cyclopedia
n. The leading genus of bivalves of the family Unionidæ: formerly used with great latitude for many species, some of which are now placed in other families as well as in other genera.
n. [lowercase] A species of this genus; any river-mussel.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. type genus of the family Unionidae
Word Usage
"The pearl (margarita) in Arab. is Lu'lu '; the "unio" or large pearl Durr, plur."