/ Dictionary / Index L leap second: Meaning and Definition of Find definitions for: leap' sec"ond Pronunciation: [key] an extra second intercalated into the world's timekeeping system about once a year, made necessary by the gradual slowing down of the earth's rotation. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. leapfrog leapt Related Content Daily Word Quiz: endear Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language