That's always open for debate and has been quite a few times on this forum. Depends on the interpretation.
There are those who go strictly by the dictionary definition (money placed/wagered on an outcome) and there are those who go by the "skill versus luck" factor (a poker tournament buy-in is like an auto race entry fee with a prize pool based on placings, etc.).
I remain squarely in the middle of both and I don't want to rehash the debate here. But I cringe when I see posts that address the issue as "black & white". No offense. Just my $.02.
I agree this is a topic for another thread (which we've had more than a few of), but I'll just say that sometimes we poker players will rip off our own nose to spite our face.
Oz is correct. And I think if we take a moment to be honest with ourselves, we cannot say that poker doesn't involve gambling. There is obviously a skill element in poker. There is obviously a luck element in poker. Any time you have a situation where luck can play a not-insignificant role in the outcome (and if one thinks luck isn't significant even in "skilled" poker then I'd call them delusional), then it qualifies as gambling. There is a ton of skill in being a successful stockbroker, futures trader, etc., but it's also highly driven by chance and other external factors that the skilled player has no control over.
What we have to get across to the die-hard anti-gamblers is that with poker, we have an opportunity to develop skill in such a way as to diminish the effect of luck. As skill increases, the role of luck decreases. It will never completely go away, but we can overcome it with skill and be victorious in the end. That just absolutely is not true with most of the casino-type gambling.
Anyway, I'm rambling on a derail, so I'll shutup now. I'm in a talky mood today for some reason...