/ Dictionary / Index A Assiniboin: Meaning and Definition of Find definitions for: As•sin•i•boin Pronunciation: (u-sin'u-boin"), [key] — pl. -boins, -boin. a member of a Siouan people of northeastern Montana and adjacent parts of Canada. the dialect of Dakota spoken by the Assiniboin Indians. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. assimilative Assiniboine Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language