(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.

Origin of backup

1775–85, Americanism; noun use of verb phrase back up
Can be confusedback up backup

Usage note

See login. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Related Words for backup

substitute, alternate, extra

Examples from the Web for backup

Contemporary Examples of backup

Historical Examples of backup

Word Origin and History for backup

see back up.

Online Etymology Dictionary, © 2010 Douglas Harper