A new company built to grow fast by finding a repeatable, scalable business model. The defining feature is the search for scale, not the age of the company or whether it uses technology.
A software company that signs its 10th customer the same way it signed its 1st, and can sign the 1,000th the same way, is a startup. A great restaurant that needs a new building for every new customer is not — it is a good small business.
Startup is not a compliment and small business is not an insult. They are different machines with different funding, different risk and different definitions of success.