By your definition then every business, every primary producer, even every government are gambling, including insider traders. None of us, no matter how much we may think otherwise, has perfect knowledge. Every activity has a certain level of risk that means failure.
What I think you need to add to your definition is an addendum that says that what you bet is significant enough that you will suffer significant harm from losing. So if you cannot afford to lose that $5 you put down on some race, then that is significant. if putting down $1,000,000 on some event and losing means nothing to you, then are you still gambling or having entertainment.
My father's advice to me from a very young age, was to treat all "bets" as a loss anda form of entertainment. So only use what you could afford to lose. if you cannot afford to lose anything, then you don't lay down resources on the expectation of "winning", that is the mug's game. So as far as day trading is concerned, follow the rules that I set out above, which are the same rules that I received from others who have actually been successful in day trading. Interestingly enough, I have had the same advice from those who were unsuccessful and they admit they broke the rules as laid out.