When Aileen Lee originally coined the term "unicorn" in late 2013, she was describing the 39 "U.S.-based software companies started since 2003 and valued at over $1 billion by public or private market investors."

Flashback: It got redefined in early 2015 by yours truly and Erin Griffith, in a cover story for Fortune, as any privately-held startup valued at $1 billion or more. At the time, we counted 80 of them.

• Ours was the definition that stuck. And, last week, the number of such companies topped 800, per CB Insights, with a cumulative valuation of around $2.6 trillion.

Why it matters: With apologies to Justin Timberlake Parker, $1 billion just isn't that cool anymore. It's not rare if there are over 800 of them, and certainly not mythical.

• Plus, there's been a flurry of startups whose valuations have been inflated by investment dollars. Isn't it more impressive to be worth $500 million on $50 million of venture capital than $1 billion on $500 million of venture capital?

We need a new word: Dragons.

• Dragons are much bigger, stronger and more awe-inspiring than unicorns. They destroy whatever's in their path, and their own destruction is viewed as catastrophic (at least if "GOT" is any guide).
• To qualify, a company must be valued at $12 billion or more, net of venture funding. Yes, it's a somewhat arbitrary figure. But it reflects the >10x "unicorn" growth since the Fortune piece, and the rapidly ascending private funding trajectory.

By the numbers: Currently, there would be 19 dragons. Of those, nine are based in the U.S.

• That's an even more exclusive club than Lee's original framing, although this is the sort of thing where less means more.
• The U.S. dragons are: Stripe, SpaceX, Instacart, Epic Games, Databricks, Rivian, Chime, Fanatics and Plaid.

The bottom line: Welcome to the age of dragons.