/ Dictionary / Index S Sea of Tranquillity: Meaning and Definition of Find definitions for: Sea' of Tranquil'lity Pronunciation: [key] See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. sea oats sea onion Related Content Daily Word Quiz: stellar Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language