/ Dictionary / Index P phototroph: Meaning and Definition of Find definitions for: pho•to•troph Pronunciation: (fō'tu-trof", -trōf"), [key] — n. Biol. any organism that uses light as its principal source of energy. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. phototransistor phototrophic bacteria Related Content Daily Word Quiz: crutiny Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language