/ Dictionary / Index I Isin: Meaning and Definition of Find definitions for: Is•in Pronunciation: (is'in), [key] — n. an ancient Sumerian city in S Iraq: archaeological site. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Isidore of Seville isinglass Related Content Daily Word Quiz: gregarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language