n. A technology company that is less than ten years old and worth more than one billion dollars.
Forget the $1 billion "unicorns" out there — the last year has been all about the rise of the $10 billion companies — both Dropbox and Chinese mobile hardware company Xiaomi both had rounds at $10 billion valuations, raising hundreds of millions of dollars.
—Lauren Hockenson, “Airbnb reportedly set to raise up to $500M at $10B valuation,” Gigaom, March 20, 2014
What's more, the number of $100 million plus funding rounds last year doubled compared to 2010, and one much-buzzed-about report shows there are more than two dozen tech startups valued at more than $1 billion. There's even a new catchphrase for such startups, which include Dropbox, Uber and Snapchat: "unicorns," denoting both their rareness and their dazzling promise.
—Peter Delevett, “Venture capital looks to be in a full-blown recovery — but is it too much, too soon?,” San Jose Mercury News, February 07, 2014
2013 (earliest)
We found 39 companies belong to what we call the "Unicorn Club" (by our definition, U.S.-based software companies started since 2003 and valued at over $1 billion by public or private market investors). …

On average, four unicorns were born per year in the past decade, with Facebook being the breakout "super-unicorn" (worth >$100 billion).
—Aileen Lee, “Welcome to the Unicorn Club: Learning From Billion-Dollar Startups,” TechCrunch, November 02, 2013