Vlad from metahead here. We answer this in the FAQ – metarepo is just a git repo that you can slice and dice any way you want while preserving history and having the ability to work on your part of the code. We went with "meta" because it's not exactly mono- or poly- – it's flexible enough so that you can make anything out of it. It also stores information about how your repos / projections relate – in that sense it's "meta" as well.