That's a good question -- in the past , I have called some of my projects micropresses, because of their size -- i.e. small runs, chapbook projects, et al. Jesse and I (with Ahadada Books) use the term "small press" because we tend to produce books with spines (although that's not always the case -- i.e. our online chapbooks). Also, we've talked about producing projects that run outside of our traditional perfect bound run.
Jay Millar's BookThug has a discussion that relates to this somewhat. Click
here for that.
What could be called a micropress is debatable I suppose. Could the term "small press" act as an umbrella term for all indpendent projects?