There are event you can predict on that even though it's not 💯 guaranteed that you're going to win, a level of certainty makes you think that you're surely going to win.
The downside of that feeling is that you might become over confident to use a big amount in the game since you're to a large extent certain that you're going to win.
Can we still say we are gambling if the event is something we are at least 90% sure that we are going to win?
When you predict something and put money into it, it's gambling. I don't know any other name or definition of what you're describing, even if you are 90% that you are going to win, there are events where bettors are betting on manipulated games, and they are sure to get a 100% result in their favour, and it's still considered gambling.
So even if you are 100% sure of winning, as long as the element of predicting and putting money in the hope of growing it, it's still gambling.
I think all references will define it that way.