Shaun McCance wrote:
It's not uncommon for software producers to have terminology guidelines that don't quite follow dictionary definitions. In the software world, we often use metaphors and re-use words with a sufficiently similar real-world meaning.
For "plug-in", the OED says:*3.* /Computing/. An easily installed item of software or hardware that can enhance or add a specific feature to a system or application.
Proper dictionaries rule ;-) -- Andrew