(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
The Collaborative International Dictionary of English (GCIDE) v.0.53Collaborative International Dictionary (GCIDE)
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. [ 1913 Webster ]