/ Dictionary / Index U underlayer: Meaning and Definition of Find definitions for: un•der•lay•er Pronunciation: (un'dur-lā"ur), [key] — n. a layer lying beneath another; substratum. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. underlay underlayment Related Content Daily Word Quiz: eureka Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language