The Collaborative International Dictionary of English v.0.48:

Aconite \Ac"o*nite\, n. [L. aconitum, Gr. ?: cf. F. aconit.]
   1. (Bot.) The herb wolfsbane, or monkshood; -- applied to any
      plant of the genus Aconitum (tribe Hellebore), all the
      species of which are poisonous.
      [1913 Webster]

   2. An extract or tincture obtained from Aconitum napellus,
      used as a poison and medicinally.
      [1913 Webster]

   Winter aconite, a plant (Eranthis hyemalis) allied to the
      aconites.
      [1913 Webster]

WordNet (r) 3.0 (2006):

aconite
    n 1: any of various usually poisonous plants of the genus
         Aconitum having tuberous roots and palmately lobed leaves
         and blue or white flowers