What is twinking, really? And when do you cross the line from a well-geared toon into a twink?

I have a level 19 hunter with the full Fang set and Venomstrike and some okay enchants. He's not in optimal gear, he doesn't have the fishing hat with the +100 HP enchant, but he's still geared well enough to occasionally top PUG BG damage charts. With this level of gear he can best an "average" level 19 toon.

Is my little hunter in druid gear a twink? Or am I just making a minimal effort (a few hours of boosting in WC) to make my BG experience more competitive and enjoyable?

In my opinion, twinking is merely the process of going into a competitive situation with the best tools available. The fact that an average toon in raggedy quest reward greens will get smoked by a toon geared and talented specifically for PVP seems to be working as intended.

I also have a larger question about why non-twink 19s run BGs. But that's another story.