To be accomplice to someone in an illegal act.
To undo one's actions.
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.
To move backwards, especially for a vehicle to do so.
To copy (data) so that it can be restored if the main copy is lost.
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.
To fill up because of a backlog.
To halt the flow or movement of something.
To provide support or the promise of support to.
To reconsider one's thoughts.
To move a vehicle backwards.
Coordinate terms: back away, back off, stand back