Decapping
Also: Depriming
Pushing the spent primer out of a fired case through the flash hole so the pocket can be cleaned and a fresh primer seated. The first step of reloading.
Decapping, also called depriming, is the first hands-on step of reloading a fired case. A pin driven through the flash hole pops the dead primer out of its pocket, clearing the case so the primer pocket can be cleaned and uniformed before a new primer goes in.
On most dies the decapping pin rides inside the sizing die, so the case is deprimed and resized in the same stroke. Some handloaders prefer a separate decapping die to knock primers out before wet tumbling, keeping grit and lubricant out of the sizing die.