/ Dictionary / Index I illuminant: Meaning and Definition of Find definitions for: il•lu•mi•nant Pronunciation: (i-l'mu-nunt), [key] — n. an illuminating agent or material. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: illuminant (Thesaurus) illuminance illuminate 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