- standing by as an alternate or auxiliary: a backup pilot
- supporting: a backup effort
- the act or result of backing up; specif.,
- an accumulation because of a stoppage
- a support or help
- Bowling a ball that follows a path opposite to that of a hook
See backup in American Heritage Dictionary 4
a. A reserve or substitute.
b. Computer Science A copy of a program or file that is stored separately from the original.
a. Support or backing.
b. Music A background accompaniment, as for a performer.
- An overflow or accumulation caused by clogging or by a stoppage: a backup in the sink; a backup of traffic at the drawbridge.
Extra; standby: a backup pilot.
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