noun, often attributive
back·​up | \ ˈbak-ˌəp How to pronounce backup (audio) \

Definition of backup

 (Entry 1 of 2)

1a : one that serves as a substitute or support I brought an extra pencil for backup. a backup plan
b : musical accompaniment The tunes include banjo and guitar backup.
c : additional personnel who provide assistance The police officer called for backup.
2 : an accumulation caused by a stoppage in the flow traffic backup
3 : a copy of computer data (such as a file or the contents of a hard drive) I made a backup copy of the file. also : the act or an instance of making a backup

back up

backed up; backing up; backing up

Definition of back up (Entry 2 of 2)

intransitive verb

: to accumulate in a congested state traffic backed up for miles

transitive verb

1 : to move into a position behind (a teammate) in order to assist on a play
3 : to make a copy of (a computer file or data) to protect against accidental loss or corruption Be sure to back up your work. also : to make copies of all the files on (a device) a program that automatically backs up your hard drive

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Synonyms for backup

Synonyms: Noun

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Examples of backup in a Sentence

Noun His role on the team is to be a backup to the regular quarterback. We have an extra radio as a backup in case this one doesn't work. We have an extra radio for backup. He provides backup for the regular quarterback. She sang backup on his CD.
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Recent Examples on the Web: Noun If the antibodies fail, killer T cells act as a backup, identifying and destroying any infected cells. Jon Cohen, Science | AAAS, "An ‘uncoordinated’ immune response may explain why COVID-19 strikes some hard, particularly the elderly," 16 Sep. 2020 Bo Scarbrough also made the initial 53-man roster as a backup. Dave Birkett, Detroit Free Press, "Detroit Lions plan fails after RB Jason Huntley claimed by Philadelphia Eagles," 6 Sep. 2020 Jackson appeared in five games as a rookie last season as a backup, and was inactive for 11 games. cleveland, "Browns claim DE Joe Jackson & NT Vincent Taylor; sign Garrett Gilbert, CB A.J. Green & K Cody Parkey to practice squad; waive Pharoah Brown & Eli Ankou," 6 Sep. 2020 The old line will be relined and used as a backup in emergencies. Susannah Bryan,, "Miles and miles of sewer pipe, waiting to get buried in Fort Lauderdale," 3 Sep. 2020 And 2019 fifth-round draft pick Ryquell Armstead will serve primarily as a backup, with Thompson being a change-of-pace, third-down option. Mark Long,, "Jaguars turn to young committee to replace Leonard Fournette," 3 Sep. 2020 He was drafted as the eventual replacement for veteran left tackle Riley Reiff, but is expected to spend his rookie season as a backup at left guard. Andrew Krammer, Star Tribune, "Ezra Cleveland's trail to Vikings promising but still full of learning curves," 29 Aug. 2020 Fletcher, who did not wait for backup, approached Taylor and tried to confiscate the bat from him, but Taylor maintained possession. Mike Brest, Washington Examiner, "California police officer charged with manslaughter in fatal shooting of black man in Walmart," 3 Sep. 2020 After the officers called for backup because the driver had a weapon visible and locked himself inside the vehicle, gunshots were exchanged. Katherine Rosenberg-douglas,, "Charges filed against 19-year-old in shooting of 2 Chicago police officers," 31 Aug. 2020 Recent Examples on the Web: Verb After getting fired from his job, Johnny decides to open the Cobra Kai studio back up, which furthers his fight with Johnny. Tamara Fuentes, Seventeen, "Meet the Cast and Characters of "Cobra Kai"," 10 Sep. 2020 But earlier this summer as cases, hospitalizations and deaths trended downward, New York began to open back up earlier this summer. Morgan Hines, USA TODAY, "Don't pronounce New York City dead just yet: Tourists are coming – and they like what they see," 28 Aug. 2020 Open the fill neck back up or crack open the system’s high point vent to let those bubbles out. Mike Allen, Popular Mechanics, "How to Maintain and Flush a Cooling System So Your Car Doesn’t Overheat," 27 Aug. 2020 Even those restaurants with outdoor spaces that have been able to open back up from the June 10 restart have not drawn enough business to reach the points in their contracts where the pier starts getting a percentage of revenues, Gardner said. Steve Johnson,, "With few visitors, Navy Pier to close down again to save money," 18 Aug. 2020 That gave officials a chance to see what would work and what wouldn’t as SMU and other colleges across the country prepared to open back up for the fall semester with the new coronavirus still a threat to communities. Dallas News, "Experiment or essential education? Texas colleges head back to school in the time of coronavirus," 15 Aug. 2020 With the curve of infections finally plateauing in late July, the church now tentatively hopes to open back up in October. Emily Wilder, The Arizona Republic, "Phoenix pastor, civil rights leader tests positive for COVID-19," 11 Aug. 2020 Open the mask back up, and tuck in the openings on the sides underneath the ear loops. Sarah Madaus, SELF, "Try This 60-Second Hack to Make Your Face Mask Fit Better," 11 Aug. 2020 Shares of the ride-hailing company have more than doubled from their March lows on investors’ confidence in a rapid recovery of the U.S. ride-share market as states open back up. Laura Forman, WSJ, "Lyft’s Recovery Looks Overheated," 7 July 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'backup.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of backup


1910, in the meaning defined at sense 1a


1801, in the meaning defined at intransitive sense

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Time Traveler for backup

Time Traveler

The first known use of backup was in 1801

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Statistics for backup

Last Updated

20 Sep 2020

Cite this Entry

“Backup.” Dictionary, Merriam-Webster, Accessed 27 Sep. 2020.

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More Definitions for backup


How to pronounce back up (audio)

English Language Learners Definition of backup

: a person or thing that can be used to replace or support another person or thing
: help or support provided by additional people or things
US : a situation in which the flow of something (such as traffic) becomes blocked


back·​up | \ ˈbak-ˌəp How to pronounce backup (audio) \

Kids Definition of backup

: a person who takes the place of or supports another The guard called for a backup.

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