/ Dictionary / Index S Sixtus V: Meaning and Definition of Find definitions for: Sixtus V Pronunciation: [key] (Felice Peretti) 1521–90, Italian ecclesiastic: pope 1585–90. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Sixtus IV sixty Related Content Daily Word Quiz: stringent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language