I'm used to thinking that a "startup" implies a small company with hockey-stick growth and eventual market domination, usually deploying large amounts of capital to fuel the growth. Otherwise it's just a sparking small business: a pizzeria is not a startup.
It seems that the internet allows for a third option: a small company that grows slowly and organically which eventually captures a significant market segment, still staying small. GitHub was like that for many years since founding. Linear apparently is another example.
I consider that it is a startup when it hasn't found a product-market fit, i.e. it is not profitable.
As soon as it is profitable, it is a normal company. Small or big.
An established company has established products and keep building/improving them. A startup does not have that: they just have ideas and try them until one works, or they run out of money. VCs consider it's worth fueling that "trial-and-error" with investments because they believe it is a competent team in a promising field. Nothing more, nothing less, it's just a lottery after that point. Just one where VCs and founders like to believe they are enlightened.
Because the first idea you try is successful does not mean you know more than the (numerous) others, but rather that you were lucky at the first try.
Is there a better word for these grow slow companies?
Businesses
If you slow grow and keep it smallish, then it’s a “lifestyle business”. That number can change but maybe $5million or less ARR. Thats enough to pay yourself and a few staff with benefits.
But like palata said above, it is a startup if hasn’t found product-market fit.
Solid? Right up to the point some funded start-up starts giving away the same thing in the hope that they can fake it until they make it and take everybody else in the same space down with them.
Linear is a really, really good product though, so it is worth paying for.
Small business?
SME, bootstrapped business.
"hypeless growth"
"Normal growth"?