(American definition, noun) Derogatory slang term that generally refers to someone who lives locally to a town, usually uttered by someone who does not. The implication is that the outside party is superior to the local populace, who are seen as inferior because of the negative stigma attached to the local environment they live in.
Most commonly used in rural college towns, where a large cultural gap exists between the students that attend and the local populace that simply happen to live there.
Townie can also be used as an adjective in the expected ways (A bar that is popular with the locals, for example, could be referred to as a "townie bar").
"I had some townie try to start a fight with me at the bar last night. I'm getting sick of these redneck locals..."