Definition of: Siouan

(s′ən) noun
A large linguistic stock of North American Indians, formerly ranging from the west banks of the Mississippi to the Rocky Mountains, and comprising the languages of the Dakota or Sioux tribes proper, those of a group including the Omaha, Osage, etc., those of the Iowa, Missouri, and Oto, also Winnebago, Mandan, Crow, Catawba, and several others now extinct.
—adjective Of or pertaining to this linguistic stock.