/ Dictionary / Index I imaginary part: Meaning and Definition of Find definitions for: imag'inary part' Pronunciation: [key] — Math. Math. the coefficient b in the complex number a + bi. Cf. real part. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. imaginary number imaginary unit Related Content Daily Word Quiz: acquiesce Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language