/ Dictionary / Index L Long Island Sound: Meaning and Definition of Find definitions for: Long" Is'land Sound' Pronunciation: [key] an arm of the Atlantic between Connecticut and Long Island. 90 mi. (145 km) long. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Long Island longitude Related Content Daily Word Quiz: ounterfeit Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language