The Collaborative International Dictionary of English v.0.48:

Snakeroot \Snake"root`\, n. (Bot.)
   Any one of several plants of different genera and species,
   most of which are (or were formerly) reputed to be
   efficacious as remedies for the bites of serpents; also, the
   roots of any of these.
   [1913 Webster]

   Note: The Virginia snakeroot is Aristolochia Serpentaria;
         black snakeroot is Sanicula, esp. Sanicula
         Marilandica, also Cimicifuga racemosa; Seneca
         snakeroot is Polygala Senega; button snakeroot is
         Liatris, also Eryngium; white snakeroot is
         Eupatorium ageratoides. The name is also applied to
         some others besides these.
         [1913 Webster]

WordNet (r) 3.0 (2006):

snakeroot
    n 1: a plant of the genus Sanicula having palmately compound
         leaves and unisexual flowers in panicled umbels followed by
         bristly fruit; reputed to have healing powers [syn:
         sanicle, snakeroot]
    2: any of various North American plants of the genus Liatris
       having racemes or panicles of small discoid flower heads
       [syn: blazing star, button snakeroot, gayfeather, gay-
       feather, snakeroot]