/ Dictionary / Index M mitral valve: Meaning and Definition of Find definitions for: mi'tral valve" Pronunciation: [key] the valve between the left atrium and left ventricle of the heart, consisting of two triangular flaps of tissue, that prevents the blood from flowing back into the atrium. Also calledCf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mitral stenosis mitre Related Content Daily Word Quiz: soporific Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language