What defines the term "spent casing"?

The term "spent casing" refers specifically to a casing that has been fired and has completed its purpose in the shooting process. Once a bullet is fired from a cartridge, the casing is ejected and is considered "spent." At this point, the casing is not suitable for further use in its current state, as it has undergone expansion and may show signs of stress or deformation.

In contrast, other options refer to casings that are either unused or in a condition where they can still be altered or utilized in some way. For instance, a casing yet to be loaded has not undergone the firing process and therefore would not be classified as "spent." A cleaned casing may be prepared for reloading but does not necessarily indicate that it has been fired. A casing used for reloading is still functional and has the potential for further use, which again does not align with the definition of a spent casing. Therefore, the definition of a spent casing is unequivocally tied to having been fired and rendered unusable in its current form.