noun 1. support given subsequently; corroboration: backup to the doctors' warnings.
2. a pent-up accumulation, especially of a liquid: the backup of flood water.
3. a reserve supply or resource; a second means of support.
a. the process of copying data to a tape, CD-ROM, etc., so that a version is available if the original data is lost, corrupted, etc.: to do the daily backup.
b. the data so copied: to retrieve files from the backup.
5. Printing the presswork on the reverse side of a printed sheet.
–adjective 6. of or relating to support given subsequently or that which so supports: a backup campaign.
7. Computers of or relating to the process of backing up: a backup tape.Also, back-up.