Source : Webster's Revised Unabridged Dictionary (1913)

Cascara buckthorn \Cas"ca*ra buck"thorn`\ (Bot.)
   The buckthorn ({Rhamnus Purshiana}) of the Pacific coast of
   the United States, which yields cascara sagrada.

Source : WordNet®

cascara buckthorn
     n : shrubby tree of the Pacific coast of the United States;
         yields cascara sagrada [syn: {bearberry}, {bearwood}, {chittamwood},
          {chittimwood}, {Rhamnus purshianus}]