"Naturalism" is indeed tricky to define, in part because it's a moving target. That's because science keeps expanding its reach, and we wrap our heads around stranger and stranger phenomena, including black holes and quantum effects.

Still, "nature" is therefore tied at least somehow to science. Whatever science can explain becomes natural to us, because science proceeds by naturalizing whatever it touches. I'd add the pragmatic, promethean (or satanic) aspect that nature is also whatever we can theoretically control with technology.

Potentially, nature is even implicitly understood in a patriarchal context, the point being that technoscience is the business of dominating reality by "naturalizing" it, by understanding its causal limits and by turning the wilderness into an artificial playground for us.

Note that that's a descriptive point. Whether we should be fully okay with that is another matter. I'm personally ambivalent about this centerpiece of modernity, so I suspect that all of us, including Graham and Sender Spike have some common ground here. I'm not quite the zealous modernist you seem to take me for.