/ Dictionary / Index B backup light: Meaning and Definition of Find definitions for: back'up light" Pronunciation: [key] a light at the rear of a motor vehicle that lights as a warning to those behind. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. backup back vent Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language