backup
back-up
noun
A copy of computer data or a reserve item for future use.
"Always keep a backup of your files."
noun
Help or support provided to someone or something.
"The police called for backup."
adjective
Providing additional support, assistance, or an alternative.
"We have a backup plan."
Thesaurus
Synonyms: patronage, championship, backing, accompaniment, support, musical accompaniment, computer backup, stand-in, reliever, relief, substitute, fill-in