In my definition and therefor expectation from my teams, a professional is a combination of two things: skills and attitude.
Skills are the capabilities and experience one brings to the table. For developers, how good they write code, for sales reps, how successful they are in closing.
Attitude is the way one brings that skills bag to work every day. In an everchanging environment, a large organization or a political office, it can be tricky. The expectation is that professionals adjust themselves to whatever is needed in that specific time, to support their's and the team's goals.
In some cases they need to take a step forward and lead a situation, in others they need to follow instructions. They need to always be team players, to show positivity in a difficult time or to walk an extra mile when needed. No exact algorithm for that, unfortunately... Be a mensch if you will, and rise up to the occasion whatever it is.
This sounds trivial but in my experience not many have that combination that will make me call them true professionals.