I've always thought of being a Hacker as more of a mindset than a badge of accomplishment. There are famous or great Hackers, like Linus or Stallman or whoever, but I've always thought of anybody who codes and has a passion for exploring new things, learning, pushing the boundaries, optimization, novel techniques, etc. as a Hacker.
And of course that's only within the context of writing software. The "hacker mentality" is really independent of coding. As far as I'm concerned, you can "hack" any sort of system, so there's no reason there couldn't be "hacker lawyers,"hacker librarians," "hacker doctors," etc.