/ Dictionary / Index G Gregory XIII: Meaning and Definition of Find definitions for: Gregory XIII Pronunciation: [key] (Ugo Buoncompagni) 1502–85, Italian ecclesiastic: pope 1572–85, educator and innovator of the modern calendar. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Gregory XII Gregory XIV Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language