Cartridge refers to ammunition. More specifically, according to gun writer Matthew Boyd, a cartridge is "the combination of the bullet, case, powder, and primer in a ready to fire configuration (the way you would buy them in a box from a gun store)."
Bibliography - Further Reading
- Party, Boston T., Boston's Gun Bible. Wyoming: American Redoubt Javelin Press, 2009 revision to 2002 edition. Chapter 9: Combat rifle cartridges. Chapter 21: Bolt action rifle cartridges. Chapter 25: Handguns - Handgun cartridges. Chapter 26: My Shopping List - Ammo for your rifle. Chapter 29: Reloading.
- Boyd, Matthew J., "Basic Firearms Terminology Defined." Guns and Shooting Online - Chuck Hawks.com, 2012. Accessed February 19, 2015