/ Dictionary / Index I irrational number: Meaning and Definition of Find definitions for: irra'tional num'ber Pronunciation: [key] — Math. Math. a number that cannot be exactly expressed as a ratio of two integers. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. irrationalize Irrawaddy Related Content Daily Word Quiz: sequester Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language