I did 7 years of full time, in-house video production for a large government agency. It used to irk the hell out of me when a client said "It's sooo professional looking!" I realize that they meant it as a compliment, but it seemed condescending!

Definition / Professional :

A professional works to receive payment for an activity (as a profession), which usually requires expertise and carries with it socially significant mores and folkways. That is to say, behaving professionally would indicate that the person's actions remain in accordance with specific rules, written or unwritten, pertaining to behavior, dress, speech, etc. By extension, the adjective professional can indicate that someone has great expertise or skill in a craft or activity.

Futher investigation lead to / THE PRO-AM REVOLUTION / THE NEW BREED !

http://www.demos.co.uk/files/proamrevolutionfinal.pdf

The term : ARTIST widely used in the film community also needs to be taken
in consideration.

My personall viewpoint / I see somebody as Vittorio Storaro (Cinematographer)
as an ARTIST.

Herman.

Not wishing to muddy the water even more, but the question could be "are you a professional professional?"

I know plenty of people making their living from the business, but some don't do it to a professional standard, I know others who do it part-time who do a better job. Here in the UK, I suspect that people tag themselves 'professional' when they carry out their work to a professional standard, with professional quality skills and experience.

Reading that back - it still doesn't really give it a proper definition!