The Collaborative International Dictionary
Rhubarb \Rhu"barb\, n. [F. rhubarbe, OF. rubarbe, rheubarbe, reubarbare, reobarbe, LL. rheubarbarum for rheum barbarum, Gr. ??? (and ??) rhubarb, from the river Rha (the Volga) on whose banks it grew. Originally, therefore, it was the barbarian plant from the Rha. Cf. Barbarous, Rhaponticine.]
(Bot.) The name of several large perennial herbs of the genus Rheum and order Polygonace[ae].
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.
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(Med.) The root of several species of Rheum, used much as a cathartic medicine.
Monk's rhubarb. (Bot.) See under Monk.
Turkey rhubarb (Med.), the roots of Rheum Emodi.
Wikipedia
Rheum emodi, commonly known as Himalayan rhubarb, is a medicinal herb used in the Indian Ayurvedic system of medicine. It belongs to the family Polygonaceae. The plant is found in the sub-alpine and alpine Himalayas at an altitude of 4000 meters.