OK Henry: I'll play.
What's your definition of a "professional" pilot?
Is it someone who's presently paid to fly, or is it someone who has been paid to fly at any time in his or her life? Or is it someone who holds a particular pilot qualification, whether or not he or she exercises all of the privileges of that qualification? If so, what is that qualification?
Be a little circumspect before you articulate your answer, lest you fall into the same trap as our volatile colleague Torres/Air Ace.