Gunner defined?

I hate people that talk in class excessively. Why is it that these people never say anything insightful? It seems fairly inevitable that whenever these people talk, they're just repeating something someone else said, or just spouting off on something completely irrelevant or inane. Personally, I think of these people as gunners. However, I've heard other people define gunners as people who not only talk excessively, but they also have to be making such a detailed point that that's what makes it irrelevant. So my question is what exactly is a gunner? And if the stupid people aren't gunners, then what technical lingo is attributed to them? It can't just be stupid people.