Can we still say we are gambling if the event is something we are at least 90% sure that we are going to win?
Of course, we can still say we're betting. Take, for example, games with odds of @1.10. You might think it's a guaranteed win, so you can bet all your money, but then lose. I've seen many cases of this. I've made some mistakes myself, placing high-odds games like @3.00 and very low-odds games like @1.15 in a parlay. Then, I'd win the high-odds games and lose the low-odds game.
From this, you learn that there's no 90% or 100% guarantee when it comes to sports betting and gambling in general. Take the recent case of the Club World Cup final, where the odds were as follows: Chelsea win @5.00 and PSG win @1.60. At the end of the game, Chelsea won. So, if you and some others were 90% confident that PSG would win, you would have lost the bet.
Yes, in as much as you are using money to get another money in terms of betting it's known as gambling .
Remember when you gamble, you are wagering your valuable things, most times funds with the reason of winning
You being sure and overconfident in your wins before staking your bet shows that you are gambling, gambling has to do with losses and wins, at times being sure of your bets could be misleading and so whatever the outcome is, it is still gambling.