Nanopublishing is the activity of putting information about one subject on a website — usually material sent in by people who use the site often and care about that subject. Think of a small niche site or an early blog, not a big newspaper. The nano- does not mean nanotechnology here; it means 'tiny', the opposite of a huge publishing company. Though actually, this is rather old internet English, more at home in early-web talk than in 2020s everyday speech. If you meet it, it is this 'very small-scale publishing' meaning.