Main Entry: back·up

Pronunciation: \-ˌəp\

Function: noun

Usage: often attributive

Date: 1951

1 a : one that serves as a substitute or support <a backup plan> b : musical accompaniment c : additional personnel who provide assistance
2 : an accumulation caused by a stoppage in the flow <traffic backup>
3 : a copy of computer data (as a file or the contents of a hard drive); also : the act or an instance of making a backup