Of a bivalve mollusc: having only one (posterior) adductor muscle; relating to or characteristic of such a mollusc. Formerly also: †belonging to the former group Monomyaria of bivalves (obsolete).
A bivalve mollusc of a type having only one (posterior) adductor muscle (e.g. an oyster).
Mid 19th century. From monomyary + -an.