[ bak-uhp ]
See synonyms for backup on
  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.

  1. an overflow or accumulation due to stoppage, malfunctioning, etc.: a sewage backup; a backup of cars at the tollbooth.

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

  3. Computers.

    • 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.

    • a procedure to follow in such an event.

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

  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.

Origin of backup

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

usage note For backup

See login.

Words that may be confused with backup

Words Nearby backup Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use backup in a sentence

British Dictionary definitions for back up

back up

  1. (tr) to support or assist

  2. (intr) cricket (of a nonstriking batsman) to move down the wicket in readiness for a run as a ball is bowled

  1. (of water) to accumulate

  2. (of traffic) to become jammed behind an accident or other obstruction

  3. computing to make a copy of (a data file), esp for storage in another place as a security copy

  4. printing to print the second side of (a sheet)

  5. (intr, usually foll by on) Australian to repeat an action immediately

  1. a support or reinforcement

    • a reserve or substitute

    • (as modifier): backup troops

  1. US and Canadian

    • musical accompaniment, esp for a pop singer

    • (as modifier): backup singer

  2. the overflow from a blocked drain or pipe

  3. computing a file or set of files copied for security purposes

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


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

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