noun, plural Assiniboins (especially collectively) Assiniboin.
a member of a Siouan people of northeastern Montana and adjacent parts of Canada.
the dialect of Dakota spoken by the Assiniboin Indians.
1675–85; < Canadian French Assiniboine < Ojibwa (Saulteaux dial.) assini·-pwa·n literally, stone Sioux (equivalent to Proto-Algonquian *aʔsenyi stone + *pwa·θa enemy tribesman)