Source : Webster's Revised Unabridged Dictionary (1913)

Cassia \Cas"sia\, n. [L. cassia and casia, Gr. ? and ?; of
   Semitic origin; cf. Heb. qets[=i][=a]h, fr. q[=a]tsa' to cut
   off, to peel off.]
   1. (Bot.) A genus of leguminous plants (herbs, shrubs, or
      trees) of many species, most of which have purgative
      qualities. The leaves of several species furnish the senna
      used in medicine.

   2. The bark of several species of {Cinnamomum} grown in
      China, etc.; Chinese cinnamon. It is imported as {cassia},
      but commonly sold as cinnamon, from which it differs more
      or less in strength and flavor, and the amount of outer
      bark attached.

   Note: The medicinal ``cassia'' (Cassia pulp) is the laxative
         pulp of the pods of a leguminous tree ({Cassia fistula}
         or Pudding-pipe tree), native in the East Indies but
         naturalized in various tropical countries.

   {Cassia bark}, the bark of {Cinnamomum cassia}, etc. The
      coarser kinds are called {Cassia lignea}, and are often
      used to adulterate true cinnamon.

   {Cassia buds}, the dried flower buds of several species of
      cinnamon ({Cinnamomum cassia}, atc..).

   {Cassia oil}, oil extracted from cassia bark and cassia buds;
      -- called also {oil of cinnamon}.

Source : WordNet®

cassia bark
     n : aromatic bark of the cassia-bark tree; less desirable as a
         spice than Ceylon cinnamon bark [syn: {Chinese cinnamon}]