Thanks for the pointer PG. Great essay. There are like a dozen gem quotes in there. I will update my post with a pointer.
To pull directly from the article a technology startup is "measurement and leverage, where measurement comes from working with a small group, and leverage from developing new techniques."
If I pull from chunks I come up with:
A small group of people inventing a new way to solve a difficult problem that is hard for others to duplicate.
It's probably easier to list a few things that are NOT technology startups (at least in 2009): consulting company, staffing company, technology product resale company, ecommerce site.
I'd already covered that here: http://www.paulgraham.com/wealth.html