A startup is a human institution designed to create new products and services under conditions of extreme uncertainty.
The Lean Startup, Eric Ries.
or,
A startup is a human institution designed to create new products, services, experiences, and relationships (solutions) under conditions of extreme uncertainty.
Glyn Davies, adapted from The Lean Startup.
Startups exist not just to make stuff, make money, or even serve customers. They exist to learn how to build a sustainable business. This learning can be validated scientifically by running frequent experiments that allow entrepreneurs to test each element of their vision.
The Lean Startup, Eric Ries.