Any of several plants of the genus Rheum, especially R. rhabarbarum, having long green or reddish acidic leafstalks that are edible when sweetened and cooked. Also called pie plant.
The dried, bitter-tasting rhizome and roots of Rheum palmatum or R. officinale of eastern Asia, used as a laxative.
Informal A quarrel, fight, or heated discussion.
[Middle English rubarbe, from Old French, from Late Latin reubarbarum, probably alteration (influenced by Greek rhēon) of rhabarbarum : rha, rhubarb (from Greek rhā, perhaps from Rhā, the Volga River) + Latin barbarum, neuter of barbarus, barbarian, foreign; see barbarous.]