A cartridge packages the bullet (also known as a "round"), gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm.
http://en.wikipedia.org/wiki/Cartridge_%28firearms%29

In various types of electronic equipment, a cartridge can refer one method of adding different functionality or content (e.g. a video game cartridge), or a method by which ...
http://en.wikipedia.org/wiki/Cartridge_%28electronics%29

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