■ noun
1》 a marine bivalve mollusc with a dark brown or purplish-black shell. [ Mytilus edulis ( edible ~ ) and other species, family Mytilidae.]
2》 a freshwater bivalve mollusc, some kinds of which produce small pearls. [Family Unionidae.]
Origin
OE mus(c)le ; ult. from late L. muscula , from L. musculus (see muscle ).