A rundown, informally known as a pickle or the hotbox, is a situation in the game of baseball that occurs when the baserunner is stranded between two bases, also known as no-man's land, and is in jeopardy of being tagged out. When the base runner attempts to advance to the next base, he is cut off by the defensive player who has a live ball and attempts to return to his previous base before being tagged out. As he is doing this, the defenseman throws the ball past the base runner to the previous base, forcing him to reverse directions again. This is repeated until the runner is put out or reaches a base safely.

A typical rundown situation in baseball showing a baserunner for the Texas Rangers as he attempts to evade the Chicago Cubs defense.

A rundown can be escaped if a fielder makes an error, the runner gets around the fielder with the ball without running out of the baseline, a fielder throws the ball elsewhere (e.g., toward home plate if another runner is trying to score), or the runner manages to get by the fielder without the ball while there is no other fielder to cover the runner's destination base.