CATHARTIC HERB is a term used to describe herbs that have a purgative effect on the body. SENNA (5 letters) is an herb from the Cassia family, which is known for its laxative properties. EPSOM (5 letters) is a type of salt made up of magnesium and sulfate, which is often used as a laxative. PHYSIC (6 letters) is an old-fashioned term for a purgative medicine or laxative. All three of these herbs are commonly used as cathartic herbs to help relieve constipation.