I think the problem a lot of people can have (especially beginner creators) is that when we hear "action", we immediately think "something fast, something dramatic, something drastic"
And that....really isn't all that it is?
I mean, that's the premise for most Action movies, but that's not all of it.
As @GusC noted -- it's focused on tension, build-up, and climax. Most good stories have that. They might not be jammed packed with flashy settings or life-changing moments. Hell, they might not be heavily conflict-based. But something is happening and we are led to a conclusion.
A good example I adore is John Carpenter's The Thing.
Yes -- there is action in the traditional sense. Explosions, murders, fighting, a bit of weaponry. But this movie focus on the tension that leads up to those moments. The buildup that makes those moments make sense. I don't watch The Thing because of the monster popping into frame. I watch it because Childs thinks Mac is the alien, because no one can trust one another, and because there is a clear conflict without flashy scenes.
As long as you are able to build up to your moments, whether it has big or small conflict or it turns out there's no real conflict at all, you have a story that has action.