/ Dictionary / Index L lightproof: Meaning and Definition of Find definitions for: light•proof Pronunciation: (līt'prf"), [key] — adj. impervious to light: a lightproof film cartridge. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: lightproof (Thesaurus) light pollution light quantum Related Content Daily Word Quiz: tenacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language