Hi,
Nowadays, with the proliferation of everything out there, it is really hard to specify a good definition, if I may say so.
There are many fine folks, even here, that do a very professional job on their work, and they are not getting credit for it, and it makes a lot of the so-called "professionals" look really bad, and wasteful in an oversize environment, when (even) some folks here would likely do a better job and organize things better.
All in all, my take on it these days differs, and "professional" really means that you take your work seriously and that you work on it, continuously, and the public affection, or derision, is not an issue, or program that bothers you ... your work, and how you define it and work it, is the "source", and thus, saying that you are not a "professional" about it, is sort of like saying that you are an amateur.
I would never EVER consider Bapu, and many other folks in this board, amateurs in any sense of the word. They are professionals of the highest caliber and I would trust them with my work to add something and polish it, and still be happy with what they did, since they would not be able to mangle it up any more than I did!
Look in the mirror. Look at your work. How professional are you about it?
There are many painters that had 1000 pieces of work before anyone noticed. There are many folks that had 150/200 songs before anyone noticed. And saying they were not "professional" is not fair to the dedication they have for their work.
The same goes for my writing, and music/film reviews. I study these things forever and love them dearly and will discuss them a lot.