Definition

Noun: 1. Support or reinforcement: The act of providing assistance, approval, or supplementary aid. 2. A reserve or substitute: A person or thing held in reserve to serve as a substitute or provide additional support if needed. 3. A copy for safekeeping: In computing, a duplicate copy of data or a file, stored separately to be used if the original is lost, damaged, or erased. 4. A musical accompaniment: A vocal or instrumental part that supports or provides background for the main musical part. 5. A blockage or accumulation: A situation where things are stopped from flowing or moving, causing an accumulation or congestion.

Usage Examples

• As support/reinforcement:
  • The police called for backup before entering the building.
  • Do you have a backup plan if it rains?
• As a reserve/substitute:
  • The injured goalkeeper was replaced by the backup.
  • She is the backup singer for the lead vocalist.
• As a copy in computing:
  • Always create a backup of your important documents.
  • I lost my essay, but fortunately I had a backup on my external drive.
• As a blockage:
  • There is a huge traffic backup on the highway due to an accident.
  • A backup in the sewer line caused flooding in the basement.

Advanced Usage

• "To have (someone's) back": This idiom is conceptually related to "backup," meaning to be ready to support or defend someone.
  • Don't worry, I have your back in the meeting.
• Functioning as an adjective: The word "backup" is commonly used attributively (before a noun) to describe something that serves as a reserve.
  • We need to test the backup generator.
  • He is the backup quarterback for the team.

Variants and Related Words

• Back up (phrasal verb): To move backwards, or to provide support or make a copy.
  • Please back up your car so I can get out.
  • You should back up your claims with evidence.
  • Remember to back up your computer files regularly.

Synonyms

• Support, aid, assistance (for meaning 1).
• Reserve, substitute, stand-in, understudy (for meaning 2).
• Copy, duplicate, archive (for meaning 3).
• Accompaniment (for meaning 4).
• Congestion, jam, blockage, stoppage (for meaning 5).

Related Phrases and Idioms

• "As a backup" / "for backup": For use as a reserve or substitute.
  • Bring an umbrella as a backup.
  • We keep extra batteries for backup.
• "Backup and running": Restored to normal operation after a failure (often used for systems or machines).
  • The server is backup and running after the crash.

Noun

1. the act of providing approval and support
   • his vigorous backing of the conservatives got him in trouble with progressives
2. (computer science) a copy of a file or directory on a separate storage device
   • he made a backup in case the original was accidentally damaged or erased
3. a musical part (vocal or instrumental) that supports or provides background for other musical parts
4. someone who takes the place of another (as when things get dangerous or difficult)
   • the star had a stand-in for dangerous scenes
   • we need extra employees for summer fill-ins
5. an accumulation caused by clogging or a stoppage
   • a traffic backup on the main street
   • he discovered a backup in the toilet