/ Dictionary / Index P phosphorous: Meaning and Definition of Find definitions for: phos•pho•rous Pronunciation: (fos'fur-us, fos-fôr'us, -fōr'-), [key] — adj. Chem. containing trivalent phosphorus. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: phosphorous (Thesaurus) phosphoroscope phosphorous acid Related Content Daily Word Quiz: cygnet Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language