/ Dictionary / Index P photoproton: Meaning and Definition of Find definitions for: pho•to•pro•ton Pronunciation: (fō"tō-prō'ton), [key] — n. Physics. a proton emitted from a nucleus during photodisintegration. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. photoprint photoreaction 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