Source : Webster's Revised Unabridged Dictionary (1913)

Senecas \Sen"e*cas\, n. pl.; sing. {Seneca}. (Ethnol.)
   A tribe of Indians who formerly inhabited a part of Western
   New York. This tribe was the most numerous and most warlike
   of the Five Nations.

   {Seneca grass}(Bot.), holy grass. See under {Holy}.

   {Seneca eil}, petroleum or naphtha.

   {Seneca root}, or {Seneca snakeroot} (Bot.), the rootstock of
      an American species of milkworth ({Polygala Senega})
      having an aromatic but bitter taste. It is often used
      medicinally as an expectorant and diuretic, and, in large
      doses, as an emetic and cathartic. [Written also {Senega
      root}, and {Seneka root}.]

Senegin \Sen"e*gin\, n. (Med. Chem.)
   A substance extracted from the rootstock of the {Polygala
   Senega} (Seneca root), and probably identical with polygalic
   acid.

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.

   Note: The Virginia snakeroot is {Aristolochia Serpentaria};
         black snakeroot is {Sanicula}, esp. {S. 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.

Source : WordNet®

Polygala senega
     n : eastern North American plant having a terminal cluster of
         small white flowers and medicinal roots [syn: {Seneca
         snakeroot}, {Seneka snakeroot}, {senga root}, {senega
         root}, {senega snakeroot}]