Example: "A traffic backup on the main street"
Example: "The star had a stand-in for dangerous scenes"
Example: "He made a backup in case the original was accidentally damaged or erased"
Example: "His vigorous backing of the conservatives got him in trouble with progressives"
Standby, reserve or extra.
Example: "I am only a backup player."
That is intended as a backup.
Example: "Make a backup copy of that file."
Supporting, reinforcing; of or related to accompaniment