/ Dictionary / Index S Sixtus I: Meaning and Definition of Find definitions for: Six•tus I Pronunciation: (siks'tus), [key] popea.d.116?–125?. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Sixtine Sixtus II 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