In all fairness, many highly successful businesses started as side projects. In my case, I started my web site about 12 years ago as a side project, and this year I expect to exceed 1 million in revenue.

I'm not sure at what point during the evolution of my side project I went from side project, to startup, to established business.

Maybe a startup should be termed as "a business that is designed to make more money than it spends."