noun 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. cassia ·noun 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.