(n) any of various plants of the genus Vernonia of tropical and warm regions of especially North America that take their name from their loose heads of purple to rose flowers that quickly take on a rusty hue, Syn. vernonia
n. (Chem.) A glucoside extracted from the root of a South African plant of the genus Vernonia, as a deliquescent powder, and used as a mild heart tonic. [ 1913 Webster ]