it refers to the act of the president of staying the execution of a convict
Stay of execution In cases where the death penalty has been imposed, a stay of execution is often sought to defer the execution of the convicted person. This may occur if new evidence is discovered that will exonerate the convicted person or in attempts to have the sentence commuted to life imprisonment. In the United States, all death sentences are automatically stayed pending a direct review by an appeals court. If the death sentence is found to have been legally sound, the stay is lifted.