Trading and Gambling are both same for me, as both are risky and waste of time, both involves risk of your money, which you can loose at any stage, so its better to stay away from both.
I do not consider trading as gambling because with trading you get something back but that is not the case with gambling.
With gambling you are not sure if you are going to win or lose.
You just said it "with gambling you are not sure if you are going to win or lose" so meaning chances of something back is possible in gambling even for low percentage.
As long as you are risking money you can considered that as a gamble. Any investment is a gamble too. It's up to the person now how they will handle and play with the gambling risk.
I agree with it, because all investments are risky too so you don't know if your investment is going to get profit because you are still basing to your skills,knowledge and as well as luck.
So trading is really considered as gambling because you are going to play for with your money in it.