Definition of shad

• n. sing. & pl. - Any one of several species of food fishes of the Herring family. The American species (Clupea sapidissima), which is abundant on the Atlantic coast and ascends the larger rivers in spring to spawn, is an important market fish. The European allice shad, or alose (C. alosa), and the twaite shad. (C. finta), are less important species.