Source : Webster's Revised Unabridged Dictionary (1913)

Shad \Shad\ (sh[a^]d), n. sing. & pl. [AS. sceadda a kind of
   fish, akin to Prov. G. schade; cf. Ir. & Gael. sgadan a
   herring, W. ysgadan herrings; all perhaps akin to E. skate a
   fish.] (Zo["o]l.)
   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. [Written also {chad}.]

   Note: The name is loosely applied, also, to several other
         fishes, as the gizzard shad (see under {Gizzard}),
         called also {mud shad}, {white-eyed shad}, and {winter
         shad}.

   {Hardboaded}, or {Yellow-tailed}, {shad}, the menhaden.

   {Hickory}, or {Tailor}, {shad}, the mattowacca.

   {Long-boned shad}, one of several species of important food
      fishes of the Bermudas and the West Indies, of the genus
      {Gerres}.

   {Shad bush} (Bot.), a name given to the North American shrubs
      or small trees of the rosaceous genus {Amelanchier} ({A.
      Canadensis}, and {A. alnifolia}) Their white racemose
      blossoms open in April or May, when the shad appear, and
      the edible berries (pomes) ripen in June or July, whence
      they are called Juneberries. The plant is also called
      {service tree}, and {Juneberry}.

   {Shad frog}, an American spotted frog ({Rana halecina}); --
      so called because it usually appears at the time when the
      shad begin to run in the rivers.

   {Trout shad}, the squeteague.

   {White shad}, the common shad.

Source : WordNet®

service tree
     n 1: medium-sized European tree resembling the rowan but bearing
          edible fruit [syn: {sorb apple}, {sorb apple tree}, {Sorbus
          domestica}]
     2: any of various North American trees or shrubs having showy
        white flowers and edible blue-black or purplish fruit
        [syn: {Juneberry}, {serviceberry}, {shadbush}, {shadblow}]