The Collaborative International Dictionary of English v.0.48:

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 Rhamnus catharticus
   are used in medicine. The latter is used for hedges.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cascara sagrada \Cas"ca*ra sa*gra"da\ (k[.a]s"k[.a]*r[.a]
   s[.a]*gr[aum]"d[.a]). [Sp.]
   Holy bark; the bark of the California buckthorn (Rhamnus
   Purshianus), used as a mild cathartic or laxative; -- called
   also cascara.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

chittamwood \chittamwood\ n.
   1. a shrubby tree of the U. S. Pacific coast (Rhamnus
      purshianus or Rhamnus purshiana), whose bark is the
      cascara sagrada, used as a mild cathartic or laxative.

   Syn: cascara, cascara buckthorn, bearberry, bearwood,
        chittimwood, Rhamnus purshianus.
        [WordNet 1.5]

   2. a deciduous tree of SE U.S. and Mexico.

   Syn: false buckthorn, chittimwood, shittimwood, black haw,
        Bumelia lanuginosa.
        [WordNet 1.5]

   3. a shrubby tree of southern U.S. (Cotinus obovatus)
      having large plumes of feathery flowers resembling puffs
      of smoke; -- called also American smoke tree.

   Syn: American smokewood, Cotinus americanus, Cotinus
        obovatus.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Rhamnus purshianus
    n 1: shrubby tree of the Pacific coast of the United States;
         yields cascara sagrada [syn: cascara buckthorn,
         bearberry, bearwood, chittamwood, chittimwood,
         Rhamnus purshianus]