Source : Webster's Revised Unabridged Dictionary (1913)

Shaddock \Shad"dock\, n. [Said to be so called from a Captain
   Shaddock, who first brought this fruit from the East Indies.]
   (Bot.)
   A tree ({Citrus decumana}) and its fruit, which is a large
   species of orange; -- called also {forbidden fruit}, and
   {pompelmous}.

Forbidden \For*bid"den\, a.
   Prohibited; interdicted.

         I kniw no spells, use no forbidden arts. --Milton.

   {Forbidden fruit}.
   (a) Any coveted unlawful pleasure, -- so called with
       reference to the forbidden fruit of the Garden of Eden.
   (b) (Bot.) A small variety of shaddock ({Citrus decumana}).
       The name is given in different places to several
       varieties of Citrus fruits.

Source : WordNet®

Citrus decumana
     n : southeastern Asian tree producing large fruits resembling
         grapefruits [syn: {pomelo}, {pomelo tree}, {pummelo}, {shaddock},
          {Citrus maxima}, {Citrus grandis}]