N-VAR
（物資、人員等的）支持，輔助
Backup consists of extra equipment, resources, or people that you can get help or support from if necessary.
例句
There is no emergency back-up immediately available...
手頭無法獲得應急支持。
Alternative treatments can provide a useful back-up to conventional treatment.
替代療法能為傳統的治療提供有效的輔助。