The Collaborative International Dictionary of English v.0.48:

Bryony \Bry"o*ny\ (br[imac]"[-o]*n[y^]), n. [L. bryonia, Gr.
   brywni`a, fr. bry`ein to swell, esp. of plants.] (Bot.)
   The common name of several cucurbitaceous plants of the genus
   Bryonia. The root of Bryonia alba (rough bryony or
   white bryony) and of Bryonia dioica is a strong,
   irritating cathartic.
   [1913 Webster]

   Black bryony, a plant (Tamus communis) so named from its
      dark glossy leaves and black root; black bindweed.
      [1913 Webster]

WordNet (r) 3.0 (2006):

white bryony
    n 1: white-flowered vine having thick roots and bearing small
         black berries; Europe to Iran [syn: white bryony,
         devil's turnip, Bryonia alba]