People may call the birth of a child or an accident in which everyone involved died except one person, a miracle. These are the kinds of miracles that have valid explanations but still people call it a miracle because it is not every day such things happen or they cannot accept the truth or they do not know the truth. If a tree falls over and the person sitting under it escaped unhurt, then it may be called a miracle. Usually people get hurt in such situations. But it is possible that all the branches miss him or the tree can fall onto another tree and stop just before hitting him. In such situations a possibility with a low probability happened. There is a reason why it happened and there is nothing supernatural about it.
There is another kind of miracle in which someone might tell something lifted off the ground by itself and started floating in the air or that a man turned into a rat etc. We know such things can't happen according to our understanding of our environment. Our understanding about our environment need not be complete in order for us to say it, for that we just need to know such a thing can't happen in such a situation. If a man turning into a rat can happen then we can include it into our understanding about our environment, given there is evidence to support it. If something has no evidence to support it and has evidence to oppose it then it can't be true. We don't have any logical reason to believe such things are possible.
We have logical abilities, memory, imagination, cognitive biases etc. We would like to think we are very logical beings but the fact is we make mistakes. We may not reconstruct the things in our memory properly and our brain may fill in the gaps to make it look logical. We may mix our imagination with our memory, or cognitive biases may affect our decisions or conclusions. Even though these are mistakes, these gave us a survival advantage and hence we have it. So what we should do is accept that we make mistakes and do the necessary corrections instead of telling there are things that logic can't explain or things beyond our understanding or there is supernatural. If somebody believes in the supernatural and wants everybody to believe him then he should be showing them valid evidence to prove it rather than asking them to make the same logical mistakes he made.
There is no supernatural. If you don't know the reasons for something then don't make up stories. Accept you don't know it and try to find out the real reason behind it. Miracles are misunderstandings or lies. They are not logical and we should discard it.