/ Dictionary / Index S Sioux: Meaning and Definition of Find definitions for: Sioux Pronunciation: (s), [key] — pl. Sioux Dakota (defs. 4, 6). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: sioux (Thesaurus) Siouan Sioux City Related Content Daily Word Quiz: serendipity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language