Ask HN: What is a startup?

On "How to make wealth" [1], pg defines A startup is a small company that takes on a hard technical problem Eric Ries' definition is: A startup is a human institution designed to deliver a new product or service under conditions of extreme uncertainty And Steven Blank's [3] definition is: A startup is an organization formed to search for a repeatable and scalable business model With these different definitions, I ask: which definition of a startup, NOT limited to these 3, most accurately reflects, in your opinion, what a startup is? Links: [1] http://paulgraham.com/wealth.html [2] http://www.startuplessonslearned.com/2010/06/what-is-startup.html [3] http://steveblank.com/2010/01/25/whats-a-startup-first-principles/