"Startup" doesn't actually mean anything, but I'll remind you that in the late '90s, there were "startups" on the NASDAQ with 8 figure market caps.
In my mind, a startup as defined by an entrepreneur is a tech-focused company shooting for rapid growth, with a liquidity event in mind.
On the other hand, a small business is built to operate for a substantial time period (sometimes generational) while providing a steady and reliable stream of income. Business growth is typically a lot slower (often intentionally controlled) but more sure-footed.
A vast portion of the multi-millionaires in this country are small-business owners...
The word "startup" to me distinguishes new independent nationwide business from corporate spinoffs, established niche companies, and regional businesses. It doesn't have any more meaning than that.
You can say startup means "shoot the moon" all you want, but I'm going to keep calling my company a bootstrapped startup.