extra help or support that you can get if necessary 增援；后援 The police had backup from the army. 警方得到了军方的增援。 🔊🔊 We can use him as a backup if one of the other players drops out. 如果有参赛者退出，我们可以用他作为替补。 🔊🔊 The hospital has a backup power supply. 这家医院有备用电源。
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computing 计算机 a copy of a file, etc. that can be used if the original is lost or damaged （文件等的）备份