The Collaborative International Dictionary of English v.0.48:

cascara \cascara\ n.
   the dried bark of the cascara buckthorn used as a laxative;
   -- called also cascara sagrada.

   Syn: chittam bark, chittem bark.
        [WordNet 1.5]

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]

WordNet (r) 3.0 (2006):

cascara
    n 1: dried bark of the cascara buckthorn used as a laxative
         [syn: cascara, cascara sagrada, chittam bark,
         chittem bark]