The way I look at it, a miracle is something contrary-wise to the course of nature, done by the power of will. If you like, something that couldn't happen without being especially willed.
13 seconds sound clip from the The Man Who Could Work Miracles (1954) movie soundboard.
You can hear this line at 00:02:41 in the DVD version of the movie.
Quote context
[...]
- Not the sort of name I personally should have associated with a gift such as he possessed.
- Thanks, I don't mind if I do.
- Same again, Miss Maybridge, and half a pound of wallet for our new friend here.
- Well, you were talking about miracles.
- Now look here, before we go any further, let's clearly understand what a miracle is.
- Well isn't it? What do you say, sir? Am I right?
- A miracle is something contrary-wise to the course of nature, done by the power of will.
- Well no, not so far as it goes.
- Very well. Now let's take a common instance.
- Well, now let me show you what I mean by a miracle.
[...]