/ Dictionary / Index I illuminance: Meaning and Definition of Find definitions for: il•lu•mi•nance Pronunciation: (i-l'mu-nuns), [key] — n. Optics. illumination (def. 6). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: illuminance (Thesaurus) illuminable illuminant Related Content Daily Word Quiz: spectral Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language