That a nice try, Prude, but the word "solely" in your definition is an add-on to the definition of a professional.
Yes, pros get paid, be they entertainers, athletes, mechanics, or...gamblers. But there is no requirement that their pay or winnings be their sole source of income.
Be it additional income or sole income, one who bets (gambles) on sports or anything else, jeopardizes their amateur standing by accepting money as winnings.
Omaha