/ Dictionary / Index R rational function: Meaning and Definition of Find definitions for: ra'tional func'tion Pronunciation: [key] — Math. Math. a function that can be written as the quotient of two polynomials with integral coefficients. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. rational form rationalism Related Content Daily Word Quiz: penchant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language