Cathartic \Ca*thar"tic\, Catharical \Ca*thar"ic*al\, a. [Gr. ?, fr. ? to cleanse, fr. ? pure; akin to F. chaste.] 1. (Med.) Cleansing the bowels; promoting evacuations by stool; purgative. 2. Of or pertaining to the purgative principle of senna, as cathartic acid.