Definition:

luck that takes the form of finding valuable or pleasant things that are not looked for

Words It Might Replace:

luck; chance; good fortune

Example:

"If there is one thing social networks and living in public have facilitated, it's serendipity. Serendipity is a good thing. It's been well documented that people who talk to strangers tend to be luckier, and this also applies to communicating with our existing networks..." – Kaila Colbin, MediaPost.com, July 15, 2011