/ Dictionary / Index V vapor barrier: Meaning and Definition of Find definitions for: va'por bar"rier Pronunciation: [key] — Building Trades. Building Trades. a layer of material, as plastic film or foil, used to protect installed insulation by retarding the transmission of moisture from the interior environment. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. vapor vaporescence Related Content Daily Word Quiz: censure Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language