Yam

n.
  1. (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 Dioscorea sativa, but several others are cultivated.
  2. (Bot.) Any one of several cultural varieties of the sweet potato.
    3. Chinese yam ,
    a plant (Dioscorea Batatas) with a long and slender tuber, hardier than most of the other species.
    Wild yam
    1. A common plant (Dioscorea villosa) of the Eastern United States, having a hard and knotty rootstock.
    2. An orchidaceous plant (Gastrodia sesamoides) of Australia and Tasmania.