A professional gambler is someone who takes and carries gambling as a profession and is a full-time gambler. Of course, you can call them professional bettors since what they basically do is use different methods to get wins and avoid losses as much as they can. Their betting patterns and bankroll management skills are too good.
Do not let us deceive ourselves, there is nothing called professional gambler, it is just not true. No gambler should see themselves as professional, they should just see it as fun and entertain themselves with it.
it is not about the day the trader may lose, there are certainty that someone that depend on gambling may see himself as professional and there later lose. The easiest way for a rich man to become poor is through gambling.