: any plant of the genus Cassia; especially: one used medicinally
: the dried leaflets or pods of various sennas (especially Cassia acutifolia and C. angustifolia) used as a purgative
Senna (Cassia didymobotrya).—Gerald Cubitt
Any of several plants, especially of the genus Cassia, in the pea family (seelegume), mostly of subtropical and tropical regions. Many are used medicinally; some yield tanbark used in preparing leather. Some sennas are among the showiest flowering trees. In the eastern U.S., wild sennas (C. hebecarpa and C. marilandica) grow up to 4 ft (1.25 m) high and have showy spikes of yellow flowers. Some species are Old World shrubs or small trees.