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 later lose. The easiest way for a rich man to become poor is through gambling.
There is no deceiving in that, there are people who do this as a profession, and being professional doesn't just mean that they earn a lot of money through it, but they do manage themselves with it since they have large bankrolls and they know how to manage their risks and their bankrolls so that they don't lose everything they have.
I totally understand that gambling if on one side can give you big winnings if you are lucky, it can also ruin you in no time if you are recklessly gambling with everything that you have and that is what professionals don't do.
Just like in trading where we have individuals we refer to as professionals same applies to gambling. A professional gambler must not bond to gambling to be referred to as professional, neither is he an addict. They're preferably seasoned gamblers that know when to to quit when he observes a red flag in his luck for the day, never desperate by having to throw in money meant for other projects regardless, and understands that gambling is a game of luck no matter how many years you have put in it doesn't mean you will always win.