/ Dictionary / Index R Río Muni: Meaning and Definition of Find definitions for: Rí•o Mu•ni Pronunciation: (rē'ô m'nē), [key] the mainland province of Equatorial Guinea on the Guinea coast: formerly the mainland portion of Spanish Guinea. 290,000; 10,040 sq. mi. (26,003 sq. km). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Rioja Rio Negro Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language