(someone or something that provides) support or help, or something that you have arranged in case your main plans, equipment, etc. go wrong

We're going to need some professional backup for this project. 要完成这项工程我们需要一些专业人员的支持。

The party is going to be outdoors, so we'll need to organize somewhere as a backup in case it rains. 晚会将在露天举行，所以我们需要安排一个备用的地方以防下雨。

Remember, your colleagues are your backup system when things go wrong. 记住，一旦出了差错，你的同事就是你的后援。

a copy of information held on a computer that is stored separately from the computer

Before we leave work each day, we make a backup of all the records we have entered into the computer that day. 每天下班之前，我们都把当天输入计算机的信息进行备份。

The department's backup disks are all stored in a different building. 该部门的备份磁盘都存放在另一栋大楼内。

a player who plays when the person who usually plays is not available

He's a backup for the Dallas Cowboys. 他是达拉斯牛仔队的替补队员。

supporting the main singer, performer, etc.

backup vocals 伴唱

Willie moves to Chicago, where he becomes a backup artist for a sultry blues singer.