a member of any of the Native American peoples formerly living in the Great Plains of the US and Canada
Plains Indian in American English
noun
a member of any of the Native American tribes, as those of the Algonquian, Athabascan, Caddoan, Kiowa, Siouan, or Uto-Aztecan linguistic families, that formerly inhabited the Great Plains. All were more or less nomadic, following the buffalo, and were often in touch with one another so that the development among them of common culture traits is noticeable