often attributive
1
a
: 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
backed up; backing up; backing up
: to accumulate in a congested state
traffic backed up for miles
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
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.
Recent Examples on the Web
Steve Conroy, Boston Herald, 15 Feb. 2026
Back home, the Elite 300 doubles as a fast 10ms UPS, offering seamless backup during storm outages or bushfire season disruptions.
—New Atlas, 15 Feb. 2026
Amanda Gerut, Fortune, 13 Feb. 2026
Past recounts and court challenges have not backed up those assertions.
—Mark Niesse For The Ajc, AJC.com, 13 Feb. 2026
See All Example Sentences for backup
Examples are automatically compiled from online sources to
show current usage.
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Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
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Noun
Connor Hellebuyck was also back between the pipes and Jake Oettinger was his backup while Jeremy Swayman, who gave up a couple of shaky goals in the win over Denmark on Saturday, was the odd man out.
—Steve Conroy, Boston Herald, 15 Feb. 2026
Back home, the Elite 300 doubles as a fast 10ms UPS, offering seamless backup during storm outages or bushfire season disruptions.
—New Atlas, 15 Feb. 2026
Verb
Bringing the price back up to its peak will mean more than doubling the stock price in the next five years.
—Amanda Gerut, Fortune, 13 Feb. 2026
Past recounts and court challenges have not backed up those assertions.
—Mark Niesse For The Ajc, AJC.com, 13 Feb. 2026
See All Example Sentences for backup
Cite this Entry
“Backup.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/backup. Accessed 16 Feb. 2026.
Copy CitationKids Definition
backup
1 of 2 noun
back·up
ˈbak-ˌəp 
1
: a person or thing that takes the place of or supports another
has a backup in case he gets sick
2
: a gathering or piling up because the flow has been stopped
a traffic backup
3
: a copy of a computer file to protect against loss of data
also
: the act or an instance of making a backup
back up
2 of 2 verb1
: to gather or pile up because the flow has been stopped
traffic backed up for miles
2
: to make a copy of (as a computer file) to protect against loss of data
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