/ Dictionary / Index P phosphonium iodide: Meaning and Definition of Find definitions for: phospho'nium i'odide Pronunciation: [key] — Chem. Chem. a colorless to slightly yellowish, crystalline, water-soluble solid, PHI, used in chemical synthesis. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. phosphonium phosphoprotein 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