backup

American  

[bak-uhp] / ˈbækˌʌp /

noun

1. a person or thing that supports or reinforces another.

2. a musician or singer or group of musicians or singers accompanying a soloist.

   a singer with a three-man backup that plays cello, bass, and guitar.

3. an overflow or accumulation due to stoppage, malfunctioning, etc..

   a sewage backup; a backup of cars at the tollbooth.

4. a person, plan, device, etc., kept in reserve to serve as a substitute, if needed.

5. Computers.

   1. a copy or duplicate version, especially of a file, program, or entire computer system, retained for use in the event that the original is in some way rendered unusable.

   2. a procedure to follow in such an event.

6. Bowling. a ball that curves in a direction corresponding to the bowling hand of the bowler.

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adjective

1. (of a person, plan, device, etc.) held in reserve as a substitute if needed.

   a backup driver; a backup generator.

2. performing a secondary or supporting function.

   A drummer and guitarist are the singer's backup musicians.

Usage

See login.

Etymology

Origin of backup

1775–85, noun use of verb phrase back up

Explanation

Backup is what someone gives when they help or support you. A brand new doctor might need some backup in the emergency room for the first few weeks. Use the noun backup when you talk about extra assistance or help. Police officers call for backup when they're not sure they can handle a situation on their own, and store cashiers need backup when things get busy and customers start lining up. Another kind of backup is the one you do on your computer — in this case, a backup is the process of copying your data in case you lose the original files.

Example Sentences

Cummins’ backup power business for AI data centers is surging, with its Power Systems segment revenue up 19% and Ebitda up 48% in Q1.

From Barron's • May 21, 2026

Today they support the apps on your phone and provide backup power to hospitals and banks during outages.

From The Wall Street Journal • May 20, 2026

After he warmed up at a gas station, backup finally arrived to fix the brakes, and he returned to the trailer and got on his way.

From Slate • May 13, 2026

Ayton’s backup Jaxson Hayes was also neutralized in Saturday’s blowout, not returning to the game after just eight minutes and 30 seconds of mostly ineffective play.

From Los Angeles Times • May 10, 2026

I wonder if the officer is watching us or calling in backup.

From "The Sky at Our Feet" by Nadia Hashimi

Related Words

• substitute