Not really. Words have meaning.
Words do have meaning, but very few words that remain in common use for extended periods of time have only one meaning.
In fact, not only does "professional" have many meanings, so does "paid," as BoulderJohn points out in his discussion of duty of care.
I have at least four different pay arrangements, each with its own set of facts and possibly its own professional risks. From time to time, a local dive shop will offer me a "paid job" to lead a local shore or inland dive; the pay is usually nominal and the tips are inconsequential. The dive shop considers me a contractor, but they have me listed on their liability policy. Sometimes, I work for one of two different charter boat operators: neither pays me, but one guarantees a minimum tip income that I've never fallen below, and neither has said anything about being covered by their liability policy, so I carry my own liability policy. Occasionally, a dive shop will charter a whole boat and "hire" me as a divemaster, but they don't pay me, and I work only for tips. Other times, I get hired by either the charter boat captain or the dive shop to guide a specific individual or couple; in this case, I get paid a guide fee by either the shop or the charter boat and I get tips, but only from the people I'm guiding. I generally assume that my own liability policy is the only one I can rely on to protect me, and I assume I have the highest duty of care when I'm hired specifically to guide particular divers. I also doubt that my contractor status would withstand scrutiny, but I'm not going to be the guy who challenges it because my occasional DM work is a pretty fun retirement gig.
Except when I'm specifically assigned to babysit someone, both the dive shop and the charter boats insist through their waivers/releases that the divers are certified divers to whom we provide taxi service and local knowledge without accepting responsibility for their dives. I hope that theory never gets tested. I have wondered, though, what would happen if a certified diver died on a regular charter. I get tipped at the end of the boat ride. If someone dies, it will be before he or she tips me, which means I was never paid or promised to be paid to care for them--and it would be before the "DM's work for tips" pitch. I hope I never learn the answer to that one, either.
For all the ambiguities, I do consider my work to be "professional" and endeavor to uphold professional standards in all of these situations.