back·upBrE/ˈbækʌp/NAmE/ˈbækʌp/noun[U, C]extrahelporsupportthatyoucangetifnecessary增援;后援◆Thepolicehadbackupfromthearmy. 警方得到了军方的增援。◆Wecanusehimasabackupifoneoftheotherplayersdropsout. 如果有参赛者退出,我们可以用他作为替补。◆abackuppowersupply备用电源(computing计算机) acopyofafile, etc. thatcanbeusediftheoriginalislostordamaged(文件等的)备份◆Alwaysmakeabackupofyourwork. 所有文件都须备份。◆abackupcopy备份文件➡ see alsoback sth↔up at backverb