from
The Collaborative International Dictionary of English v.0.48
Yam \Yam\ (y[a^]m), n. [Pg. inhame, probably from some native
name.]
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.
[1913 Webster]
2. (Bot.) Any one of several cultural varieties of the sweet
potato. [U. S.]
[Webster 1913 Suppl.]
{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.
[1913 Webster]