I think the term startup describes an unproven business.
You can have all the funding in the world, or have been operating for 10+ years, and it still may not be clear that you've got a viable business.
I do think it's important to distinguish between startups and growth companies. Facebook is no longer a startup, it clearly (to me at least -- though I'm sure this will be contentious) is a viable business, all that extra VC is about fueling mega-growth.
You can have all the funding in the world, or have been operating for 10+ years, and it still may not be clear that you've got a viable business.
I do think it's important to distinguish between startups and growth companies. Facebook is no longer a startup, it clearly (to me at least -- though I'm sure this will be contentious) is a viable business, all that extra VC is about fueling mega-growth.