What: Shares of Wynn Resorts, Limited (WYNN 1.44%) jumped as much as 18% today after founder and CEO Steve Wynn disclosed he had bought 1 million shares of stock.

So what: Between Dec. 4 and Dec. 8, Steve Wynn bought 1 million shares of stock and increased his stake in Wynn Resorts by about 10%. His motivation wasn't given, but with shares trading 56% lower than they were a year ago (as of yesterday's close), he clearly thought shares were undervalued.

Insider buying can be a bullish sign for stocks, and with an insider as intimately involved with a business as Steve Wynn, investors clearly see it as a good sign.  

Now what: There are certainly a lot of unknowns at Wynn Resorts heading into 2016, but with Wynn Palace only a few months from completion, Wynn sees good performance ahead. Investors should take this as a data point in their analysis, though buying on Wynn's move alone wouldn't be wise. He has a large stake in the company and this could be a move to grab even more control rather than a sign that a Macau recovery is on the horizon. Still, it's an interesting move and makes Wynn Resorts a stock to watch closely in 2016.