This can be a very tricky question to answer.
Yes and no with gambling you have some idea what your up against.
In trading well it can be emotionally driven or be powered by speculative investment in things.
Which if they get scared well you could lose a lot of money ive seen it happen many times.
Well it can be said easily with, it depends on the person who is trading. If the person is trading blindly, meaning that person does not have any knowledge about trading at all then it is considered as gamble. He is betting on his luck in buying random stocks and wish it increase in price.