n. pl.; sing. Seneca /sing>. (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. [ 1913 Webster ]

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. ] [ 1913 Webster ]