Source : Webster's Revised Unabridged Dictionary (1913)

Dogbane \Dog"bane`\, n. [Said to be poisonous to dogs. Cf.
   {Apocynaceous}.] (Bot.)
   A small genus of perennial herbaceous plants, with poisonous
   milky juice, bearing slender pods pods in pairs.

Source : WordNet®

dogbane
     n : any of several poisonous perennial plants of the genus
         Apocynum having acrid milky juice and bell-shaped white
         or pink flowers and a very bitter root