What, exactly, is a startup?

Two definitions of startups:

One from an excellent piece by Steve Blank on why companies are not startups:

“a startup is a temporary organization designed to search for a repeatable and scalable business model. The corollary for an enterprise is:

A company is a permanent organization designed to execute a repeatable and scalable business model. Once you understand that existing companies are designed to execute then you can see why they have a hard time with continuous and disruptive innovation.

Another is in this great piece by Paul Graham in which he suggests Startup = Growth:

“A startup is a company designed to grow fast. Being newly founded does not in itself make a company a startup. Nor is it necessary for a startup to work on technology, or take venture funding, or have some sort of “exit.” The only essential thing is growth. Everything else we associate with startups follows from growth.”

Not sure what to make of these two definitions…but they sure are interesting when placed side-by-side.