Rhizome

['raɪzəʊm] or ['raɪzom]

(noun.) a horizontal plant stem with shoots above and roots below serving as a reproductive structure.

Typed by Lloyd--From WordNet

(n.) A rootstock. See Rootstock.

Edited by Darrell

n. a root-stock an underground stem when its shape is cylindrical ending in a bud and bearing leaves or scales.—Also Rhizō′ma.

Typed by Elroy