Plug-in (computing)

Software component that extends the functionality of existing software

In computing, a plug-in (also spelled plugin), add-in (also addin, add-on, or addon) or extension is a software component that extends the functionality of an existing software system without requiring the system to be re-built. A plug-in feature is one way that a system can be customizable.

From Wikipedia, under CC BY-SA. More on occurri.