Oxford Dictionary: the occurrence and development of events by chance in a happy or beneficial way
Cambridge English Dictionary: the fact of finding interesting or valuable things by chance
Collins English Dictionary: the faculty of making fortunate discoveries by accident
It’s interesting to see a word being described in a slightly different way, but I think when you feel you happened to encounter anything that will make you think about the word immediately, that thing should be very amazing, wonderful, or rarely seen to you.
I took this photo purely by chance. That was not the place I intended to go, it’s just “there" when I passed the streets nearby and suddenly, I found this brick building with a traditional style. It just made me feel I was walking into an early 20th century setting, and later there might be some people coming out from the building and wearing traditional costumes… But it’s in fact a building inside a university, and I just happened to walk by through the backside. Still, I felt lucky to capture this scene. I guess this could be a moment of serendipity.