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n. (Bot.) A large, esculent, farinaceous tuber of various climbing plants of the genus Dioscorea; also, the plants themselves. Mostly natives of warm climates. The plants have netted-veined, petioled leaves, and pods with three broad wings. The commonest species is D. sativa, but several others are cultivated. Chinese yam, a plant (Dioscorea Batatas) with a long and slender tuber, hardier than most of the other species.

 - Wild yam. (a) A common plant (Dioscorea villosa) of the Eastern United States, having a hard and knotty rootstock. (b) An orchidaceous plant (Gastrodia sesamoides) of Australia and Tasmania.