/ Dictionary / Index P photoactinic: Meaning and Definition of Find definitions for: pho•to•ac•tin•ic Pronunciation: (fō"tō-ak-tin'ik), [key] — adj. emitting radiation having the chemical effects of light and ultraviolet rays, as on a photographic film. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. photo photoactivation Related Content Daily Word Quiz: fidelity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language