Definition of rhubarb

• n. - The name of several large perennial herbs of the genus Rheum and order Polygonaceae.
• n. - The large and fleshy leafstalks of Rheum Rhaponticum and other species of the same genus. They are pleasantly acid, and are used in cookery. Called also pieplant.
• n. - The root of several species of Rheum, used much as a cathartic medicine.