Source : Webster's Revised Unabridged Dictionary (1913)

Rhamnus \Rham"nus\, n. [NL., from Gr. "ra`mnos a kind of prickly
   shrub; cf. L. rhamnos.] (Bot.)
   A genus of shrubs and small trees; buckthorn. The California
   {Rhamnus Purshianus} and the European {R. catharticus} are
   used in medicine. The latter is used for hedges.

Cascara sagrada \Cas"ca*ra sa*gra"da\ [Sp.]
   Holy bark; the bark of the California buckthorn ({Rhamnus
   Purshianus}), used as a mild cathartic or laxative.

Source : WordNet®

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