/ Dictionary / Index P phosphonium: Meaning and Definition of Find definitions for: phos•pho•ni•um Pronunciation: (fos-fō'nē-um), [key] — n. Chem. the positively charged group PH⫀. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. phospholipid bilayer phosphonium iodide Related Content Daily Word Quiz: opulent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language