Source : Webster's Revised Unabridged Dictionary (1913)

Sorb \Sorb\, n.[L. sorbus the tree, sorbum the fruit; cf. F.
   sorbe. See {Service tree}.] (Bot.)
   (a) The wild service tree ({Pyrus torminalis}) of Europe;
       also, the rowan tree.
   (b) The fruit of these trees.

   {Sorb apple}, the fruit of the sorb, or wild service tree.

   {Sorb tree}, the wild service tree.

Source : WordNet®

sorb apple
     n 1: medium-sized European tree resembling the rowan but bearing
          edible fruit [syn: {service tree}, {sorb apple tree}, {Sorbus
          domestica}]
     2: acid gritty-textured fruit [syn: {sorb}]