snakeroot

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various plants, such as black cohosh, rattlesnake master, sanicle, or wild ginger, having roots reputed to cure snakebite.

from The Century Dictionary.

• noun A name of numerous plants of different genera, whose root either has a snake-like appearance, or has sometimes been regarded as a remedy for snakes' bites, or both. Several have a medicinal value. Compare rattlesnake-master and rattlesnake-root.
• noun The black cohosh, Cimicifuga racemosa. whose root is an officinal remedy used in chorea, and formerly for rheumatism.
• noun A general name for the species of Liatris: so called from the button-shaped corms, or from the button-like heads of some species, and from their reputed remedial property. (See cut under Liatris.) L. spicata, also called gay-feather, is said to have diuretic and other properties.

from the GNU version of the Collaborative International Dictionary of English.

• noun (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any member of the genus Ageratina of perennials and rounded shrubs from the sunflower family, growing mainly in the warmer regions of the Americas.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any of various North American plants of the genus Liatris having racemes or panicles of small discoid flower heads
• noun 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