| Noun | 1. | freshwater mussel - bivalve mollusk abundant in rivers of central United Statesmussel - marine or freshwater bivalve mollusk that lives attached to rocks etc. pearly-shelled mussel - the pearly lining of the dark shells is a source of mother-of-pearl thin-shelled mussel - mussel with thin fragile shells having only rudimentary hinge teeth Dreissena polymorpha, zebra mussel - inch long mollusk imported accidentally from Europe; clogs utility inlet pipes and feeds on edible freshwater mussels |