n 1  :  any of several plants of the genus Rheum having large leaves with thick succulent petioles often used as food  2  :  the dried rhizome and roots of any of several rhubarbs (esp. Rheum officinale and R. palmatum) grown in China and Tibet and used as a purgative and stomachic .
 
 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2004.