[ bak-uhp ]
/ ˈbækˌʌp /
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(of a person, plan, device, etc.) held in reserve as a substitute if needed: a backup driver; a backup generator.
performing a secondary or supporting function: A drummer and guitarist are the singer's backup musicians.
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Which form is used to state an obligation or duty someone has?

Origin of backup

1775–85, Americanism; noun use of verb phrase back up

usage note for backup

See login.


back up, backup
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What does backup mean?

A backup is a person or thing that supports another, as in My role as the backup for the sales team is to take calls when the rest of the team is busy.

Backup is a noun form of the verb phrase back up, which means to support or assist.

A backup is also a person or thing kept in reserve as a substitute, as in The backup for the cake I’m making is the apple pie in the freezer.

A backup is also an overflow or accumulation caused by a blockage or stoppage, such as a car backup on the highway when there’s an accident further ahead on the road.

Backup also describes a person or thing that acts as a backup, as with backup dancers, a backup generator, a backup food supply, and a backup plan.

Example: Bring in some backup workers to help assist the customers lined up outside the door.

Where does backup come from?

The first records of the term backup come from the 1770s. It comes from the verb phrase back up, meaning “to support or assist.”

In computing, backup has a specific meaning. It refers to a copy of the data, such as photos and text files, created in case of data loss or technology malfunction. More technically, a backup on a computer refers to a compressed copy of all files on a system that is stored to an external disk and that can be used to rewrite a system’s files back to the time of the backup.

Did you know … ?

What are some synonyms for backup?

What are some words that share a root or word element with backup

What are some words that often get used in discussing backup?

How is backup used in real life?

Backup is a common word used in reference to something that supports or that overflows.

Try using backup!

Is backup used correctly in the following sentence?

Be sure to backup all photos on your phone so you don’t lose them.

How to use backup in a sentence

British Dictionary definitions for backup

back up

verb (adverb)
noun backup
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Idioms and Phrases with backup

back up


Move or drive a vehicle backward, as in He told her to back up into the garage. [First half of 1800s]


Bring or come to a standstill, as in The water had backed up in the drains, or The accident had backed up traffic for miles. [First half of 1800s]


Support or strengthen, as in The photos were backed up with heavy cardboard so they couldn't be bent, or I'll back up that statement of yours. [Second half of 1700s]


Duplicate a file or program so that the original is not lost. For example, Every computer manual warns you to back up your work frequently in case of a power outage or computer failure. [Second half of 1900s]

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.