Definition of: eupatorium

(y′pə·tôr′ē·əm, -tō′rē-) noun
Any plant of the large, principally American genus (Eupatorium) of herbaceous or shrubby plants of the composite family, the thoroughworts, with mainly aromatic or bitter leaves and numerous corymbose heads of small flowers, as the joe-pye-weed, the boneset, the white snakeroot, and hemp agrimony. [<NL <Gk. eupatorion agrimony; named after Mithridates VI, called Eupator <eu- good + patēr father]