Gamble means taking a risk for anticipated or potential gain or reward. now the keyword here is anticipated or potential, here, the gain or reward is anticipated and not definite, that is to say, your expectations are not certain, comparing it to trading we can say it's the same.
You're only analyzing that based on semantics and it's a wrong way to go about it. If only you can look at it from the angle that in gambling, the anticipation isn't based on any product to be exchanged. Nothing of that nature. With trading, there's an anticipation based on one product price going up while the other is coming down. There's actually buying and selling going on.
Then I paused again and asked, but if this is it, then life itself is a gamble right, but another definition says, risking money for anticipated monetary gain, hmmm and that is definitely similar to sports gambling.
Life is a risk, not gambling. You've to know that not all risky activity is gambling.
Life is thought to be risky because no one truly can say what happens next each time they sleep off, cross the road, drive out, go shopping, drop kids off school etc. Anything we can predetermine its outcome isn't risky. But in all that, we haven't gambled doing any of the above.