What was said above asked for the meaning of the song and not for comments. So here's what I have to say.
It's about unexpected happening. It meant seeing someone you'd never even think about to begin with. Maybe a prince and in the song's case, Romeo. Then you'll meet, know each other in the least possible and extraordinary way both of you really didn't encounter before. Then that's when you'll wait. Juliet waiting for Romeo and then feeling like she's about to give up. True indeed. But then comes the surprise, a very memorable scene even in the music video when Romeo just came and told her a miracle and what's more was it already happened before she knew it.