Tom and Mary were my backup singers back when I used to perform.
It's wise to make data backup on your computer every now and again.
There was a backup on the highway because of an accident.
Bring backup. Have you made a backup of that document?
There must be another backup.
It’s a good idea to save this file as backup.
Jane radioed the dispatcher for backup.
No problem. If X happens, we have Y as a backup.