Well, I disagree with the second part of your post, andrea. If for the sake of the argument we assume that fantasy novels describe alternative universes, then I argue that what ever is possible in those alternate worlds and not in ours due to difference in physical laws, shouldn't be called magic either. Not even if the AU's people can shoot fireballs from their fingertips, as long as they do it according to this particular universe's laws.
Yes, some fantasy authors go to great lenghts to explain the "how" of what looks like magic from our perspective, but as long as the final point of their argumentation is "because it's possible due to different laws of physics", then it shouldn't be called magic. You could say that It's not my business to tell people what to call magic, but I find this clarification necessary to resolve this topic's challenge. Not to mention that it'd be nice if people didn't use the same word for defining what now reached three different ideas.
So let's not call magic what can be called unknown, or undiscovered.
Let's not call magic what can be logically derived from given universe's laws of physics, however exotic they could be.
Let's define magic as something that is: a)able to alter the world's existence, it's universal laws if you want, b)it's chaotic and unpredictable, differentiating it from just a "higher level" of universal laws.
Do note, that this definition does not require of an author to abandon logic when describing his universe. As I've shown you earlier, when describing Babylonian's cosmogony(which is really just one of many similar ones), existence of magic can be, and historically had been, logically justified. Just keep in mind that the final reason for it's existence does not, as with technology-magic, lie within laws of the universe, but within the philosophy behind world's creation.
@Sean M.: yeah, the nomenclature needs being sorted out for a meaningfull conversation.