DCHP-1 Online
Plain(s) Indian 
n. a member of a of several tribes of Indians inhabiting the prairies, as the Blackfoot, Assiniboine, and Plains Cree.
See also: horse Indian (def. 2) Prairie Indian
- 1697 (1929) . . . about four a clock some plain indians arrived at the fort. . . .
- 1844 (1955) The plains Indians are in a state of warfare, and there is a certain degree of danger in a single boat or canoe passing through their country.
- 1878 He considers the success of this attempt of the Plain Indians to settle down to the routine of the whiteman's life . . . as most successful and gratifying.
- 1957 For the pedestrian Plains Indians, without a horse, the dog was a beast of burden.
- 1697 (1929) . . . about four a clock some plain indians arrived at the fort. . . .