It depends on which type of trade you're in, actually lot of skills required to get success in trading. Partially we can accept that the trading as gambling because along with skills and knowledge luck matters in trading. Once if anybody tastes success while trading by sheer luck they can term it as gambling.
Generally the fact is that many traders belong to gambling as well as their direct occupation. Reality of trade can also bring aesthetic pleasure and passion from the fact that you are at risk.