The Collaborative International Dictionary of English v.0.48:

Wolfsbane \Wolfs"bane`\, n. (Bot.)
   A poisonous plant (Aconitum Lycoctonum), a kind of
   monkshood; also, by extension, any plant or species of the
   genus Aconitum. See Aconite.
   [1913 Webster]

WordNet (r) 3.0 (2006):

wolfsbane
    n 1: poisonous Eurasian perennial herb with broad rounded leaves
         and yellow flowers and fibrous rootstock [syn: wolfsbane,
         wolfbane, wolf's bane, Aconitum lycoctonum]