The Collaborative International Dictionary of English v.0.48:

Boneset \Bone"set`\ (-s[e^]t`), n. (Bot.)
   A medicinal plant, the thoroughwort (Eupatorium
   perfoliatum). Its properties are diaphoretic and tonic.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Eupatorium perfoliatum
    n 1: perennial herb of southeastern United States having white-
         rayed flower heads; formerly used as in folk medicine [syn:
         boneset, agueweed, thoroughwort, Eupatorium
         perfoliatum]