/ Dictionary / Index I imaginary axis: Meaning and Definition of Find definitions for: imag'inary ax'is Pronunciation: [key] — Math. Math. the vertical axis in an Argand diagram. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. imaginary imaginary number 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