Just by the name itself Forex Trading - it is not gambling, it is simply trading.
However, most of the forex brokers today are fueled by greed in making money, they are advertising that you can be rich by trading forex full-time or even part-time and yet, 90 to 95% of the retail traders lose money. Forex trading is not for everyone, and most of these so-called retail traders are better off buying a lottery ticket.
Broker leverage - Some brokers out there makes you believe that high leverage is good for you. They offer the clients from 1:100, 1:200, 1:500 up to ridiculous leverage of 1:5000 - just imagine what these brokers are up to. They want their clients to lose so that they can take home their deposit as soon as you lose.
They advertise that you can be rich and earn thousands and even millions in just a few months of trading and that what makes forex trading very dangerous - you will take a "very bad leap in the dark" if you believe that.
CONCLUSION
Forex trading is not gambling when you do not use so much leverage.
Forex trading is not gambling when you have the skill of technical analysis.
Forex trading is not gambling when you are a strong discipline.
Forex Trading is not gambling when you have a profitable trading plan.
Forex trading is not gambling when you have enough practice in your demo account before going live.