The Collaborative International Dictionary of English v.0.48:

cancerweed \cancerweed\ n.
   a sage of eastern U. S. (Salvia lyrata).

   Syn: cancer weed.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

cancerweed
    n 1: sage of eastern United States [syn: cancerweed, cancer
         weed, Salvia lyrata]