back-up

Universal Words noun [U,C] 1 extra help or support that you can get if necessary: The police had back-up from the army. * We can use him as a back-up if one of the other players drops out. * a back-up power supply 2 (computing) a copy of a file, etc. that can be used if the original is lost or damaged: Always make a back-up of your work. * a back-up copy