- any of a number of bivalve molluscs with a brown or purplish-black shell:
- a marine bivalve which uses byssus threads to anchor to a firm surface (family Mytilidae, order Mytiloidea), including the edible mussel (Mytilus edulis). a freshwater bivalve which typically lies on the bed of a river, some species forming small pearls (family Unionidae, order Unionoida).
Old English mus(c)le, superseded by forms from Middle Low German mussel, Middle Dutch mosscele; ultimately from late Latin muscula, from Latin musculus (see muscle)
Do not confuse muscle with mussel. Muscle means 'the tissue that moves a body part' (tone up your thigh muscles), whereas mussel means 'a shellfish' (fish soup with mussels and clams).