/ Dictionary / Index P phototube: Meaning and Definition of Find definitions for: pho•to•tube Pronunciation: (fō'tu-tb", -tyb"), [key] — n. Electronics. an electron tube with a photosensitive cathode, used like a photocell. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. phototropism phototype 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