The Collaborative International Dictionary of English v.0.48:

Ginseng \Gin"seng\, n. [Chinese.] (Bot.)
   A plant of the genus Aralia, the root of which is highly
   valued as a medicine among the Chinese. The Chinese plant
   (Aralia Schinseng) has become so rare that the American
   (A. quinquefolia) has largely taken its place, and its root
   is now an article of export from America to China. The root,
   when dry, is of a yellowish white color, with a sweetness in
   the taste somewhat resembling that of licorice, combined with
   a slight aromatic bitterness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ginseng
    n 1: aromatic root of ginseng plants
    2: Chinese herb with palmately compound leaves and small
       greenish flowers and forked aromatic roots believed to have
       medicinal powers [syn: ginseng, nin-sin, Panax ginseng,
       Panax schinseng, Panax pseudoginseng]