back-up

n 1 [U] support; reserve 支持; 支援; 後备: The police had military back-up. 警方有军队作後盾. * [attrib 作定语] back-up services 善後服务 * the back-up team of a racing driver 赛车手的後勤队. 2 [U, C] (computing 计) (making a) copy of a file, program, etc for use in case the original is lost or damaged （制作）（文件、程序等的）复制件（以备原件丢失或损坏时使用）: [attrib 作定语] a back-up disc 复制件磁盘.

bacillus, back, back and forth, back away, back down, back down off, back down/off, back number, back of, back out of, back road, back room, back seat, back talk, back up, back-bench, back-bencher, back-breaking, back-formation, back-pedal, back-yard, backache, backbite, backbiter, backbiting, backbone, backchat, backcloth, backcomb (also tease), backdate, backdrop, backer, backfire, backgammon, background, backhand, backhanded, backhander, backing, backlash,