A business is a startup when its goal is to raise investment with the understanding that it will use all the money towards rapid, aggressive growth, and then raise the next, much bigger round of investment, or get acquired, or go bust.

What's the current term then for a newly founded business that is pursuing some other strategy? For instance, bootstrapping to organic growth, or self-funding toward a long-term profitable "lifestyle" business?

A "new business" or a "small enterprise"

Solid definition. Being on the VC treadmill, and all of the “vibes” that come with that, is really what it boils down to.

I like to say a startup is a business where growth is far and away the primary goal and it becomes a regular business as that shifts toward revenue or stability or specialization. I don't think it HAS to be VC but a big chunk of VC cash is a great way to bet everything on growth so it might be the defacto definition anyway and I'm splitting hairs.

By your definition OpenAI and Databricks are startups.

My definition is that a startup hasn't found its product-market fit yet. As soon as you are profitable, you're a business, whether or not you take investments to grow faster.

You're a startup when you're testing a new business model. If you realise that it works, then you're a business.

Seeking or taking funding is my personal rule-of-thumb.