/ Dictionary / Index S sinsyne: Meaning and Definition of Find definitions for: sin•syne Pronunciation: (sin'sīn), [key] — adv. Scot. and North Eng. from that time; since then. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Sinsiang sin tax Related Content Daily Word Quiz: procrastinate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language