backup · noun /ˈbæk.ʌp/
backup (EXTRA HELP)
B2 C or U extra help, support or equipment which is available if you need it
Dictionary example:
Medical staff are on call to provide backup in case of an emergency.
Learner example:
I'm sure that most business people have battery back-up and a very good knowledge of when the laptop battery needs to recharge. (First Certificate in English; B2; Swedish)
backup (COPY)
B2 C a copy of information that is held on a computer, which is stored separately from the computer
Dictionary examples:
Before we leave work each day, we make a backup of all the records we have entered into the computer that day.
The department's backup disks are all stored in a different building.
Learner example:
Seems he had made a copy in a special file in a back-up memory. (First Certificate in English; B2; Portuguese)