I'm going to need to see that definition, because I think it can also apply to someone who volunteers an answer and is then pleased when the prof agrees with them. But both are required elements, you see: Volunteering followed by pride in a job well done. Anyone who knows the answer can volunteer to answer a question - that's easy.
I would have to say that offering an answer and being pleased with the result is a necessary, but not sufficient part of being a gunner. Anyone who volunteers an answer and is right will probably be happy about it. In my book, that does not constitute a gunner. Maybe we need to have a discussion on the exact requirements of being a gunner.
I would put forth the following requirements. Feel free to add to the list.
1. Offering an answer and being pleased with the result.
2. Liking the sound of your own voice.
3. Desire that you seem extremely intelligent (to the professor and/or classmates) (this is one reason why I don't consider myself a gunner, I don't volunteer answers to sound smart I answer because I'm interested in the discussion and the ideas put forth, etc.).
4. Commenting/Answering a question at least every other class period.
5. Sitting in the front row (unless the professor makes the seating chart before class starts).
6. Douchiness in general.
7. A seemingly large lack of awareness that you are annoying others/talking too much.