/ Dictionary / Index P Pius IV: Meaning and Definition of Find definitions for: Pius IV Pronunciation: [key] (Giovanni Angelo Medici) 1499–1565, Italian ecclesiastic: pope 1559–65. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Pius III Pius V Related Content Daily Word Quiz: tactful Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language