/ Dictionary / Index U underlap: Meaning and Definition of Find definitions for: un•der•lap Pronunciation: (un"dur-lap'), [key] — -lapped, -lap•ping. to extend partly under. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. underlaid underlay Related Content Daily Word Quiz: frugal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language