/ Dictionary / Index P photoreactivation: Meaning and Definition of Find definitions for: pho•to•re•ac•ti•va•tion Pronunciation: (fō"tō-rē-ak"tu-vā'shun), [key] — n. Biochem. a process that repairs DNA damaged by ultraviolet light using an enzyme that requires visible light. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. photoreaction photorealism Related Content Daily Word Quiz: pugilist Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language