back up

To move backwards, especially for a vehicle to do so.

“That beeping sound indicates that the truck is backing up.”

To move a vehicle backwards.

“Back up the car a little, you're blocking the driveway.”

To undo one's actions.

“I couldn't see how to finish the project, so I backed up and tried it another way.”

To reconsider one's thoughts.

“This isn't working. Let's back up and think about it.”

To copy (data) so that it can be restored if the main copy is lost.

“Back up your documents folder before applying the update.”

To provide support or the promise of support to.

“When he said I wasn't there, I told him I was, and my buddy backed me up.”

For the non-striker to take a few steps down the pitch, in preparation to taking a run, just as the bowler bowls the ball.

For a fielder to position himself behind the wicket (relative to a team-mate who is throwing the ball at the wicket) so as to stop the ball, and prevent overthrows.

(of a blockage) To halt the flow or movement of something.

“When I flushed the toilet, the plumbing backed up and burst.”

To fill up because of a backlog.