Stop-second is a mechanism that stops the watch and therefore its seconds hand in order to adjust the time to the nearest second.

This system often works with the help of a blade that simply stops the balance when the crown is put in the time setting position. Some have gone so far as to integrate this mechanism on tourbillons. There is also an even more sophisticated system which is the stop-second and reset.

On a quality watch not equipped with a stop-second the stop of the second can also often be achieved by a correctly adjusted indenting by making the hands go backwards.