backupsn.备份backupn.后备backup of each other互为备用性backup roll extractor支承辊换辊装置backup system library后备系统库Backup Bus Controller备份总线控制器Backup Flight Control备用飞行控制backup instrumentation备用检测仪器backup signal location候补信号点backup yaw damper unit备用偏航阻尼器backup tape generation备份磁带生成backup power indicator后备电源指示灯

back upvi.(因积聚而)拥堵；堵塞vt.支持；援助；倒退；（资料）备份