Merriam-Webster Collegiate Dictionary - rhubarb

 noun  Etymology: Middle English rubarbe, from Anglo-French reubarbe, from Medieval Latin reubarbarum, alteration of rha barbarum, literally, barbarian ~  Date: 15th century  1. any of a genus (Rheum) of Asian plants of the buckwheat family having large leaves with thick succulent petioles often used as food; also the petioles of ~  2. the dried rhizome and roots of any of several ~s (as Rheum officinale and R. palmatum) grown in China and Tibet and used as a purgative and stomachic  3. a heated dispute or controversy RHUMB LINE  noun  Etymology: Spanish rumbo  Date: 1669 a line on the surface of the earth that follows a single compass bearing and makes equal oblique angles with all meridians — called also loxodrome