back up

verb

backed up; backing up; backing up

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

2

: hold back sense 1

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 back up in a Sentence

Recent Examples on the Web

One big question now is how much money the national GOP is willing to spend to back up Desmond, especially given that Democratic advantage, said Thad Kousser, a political science professor at UC San Diego. —Lucas Robinson, San Diego Union-Tribune, 4 June 2026

The first farmers market in California was right here in the Bay Area — when canneries were backed up during World War II and growers in the North Bay had nowhere to send their fruit. —John Metcalfe, Mercury News, 4 June 2026

Once this upper-level system moves out, temperatures quickly heat right back up into the 90s. —Michael Autovino, CBS News, 4 June 2026

Pulsetto’s own marketing leans on internal numbers to back up the timeline. —Samantha Agate, Kansas City Star, 4 June 2026

Word History

First Known Use

1801, in the meaning defined at intransitive sense

Rhymes for back up

• backup
• blowup
• breakup
• buildup
• checkup
• cleanup
• holdup
• hookup
• lineup
• lockup
• makeup
• markup

Kids 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 verb

1

: 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