My working definition is something like “pre-product-market-fit” or “hockey sticking” growth. Once you saturate your market and have to fight for every percentage of growth (or are so big that new things can’t make a big impact even if they are exploding in their niche) then you’re no longer a startup

This also implies that linear growth companies aren’t startups, they’re SMBs. This is probably controversial and definitely valley/VC centric.

pre-exit, I presume.