In short, Wolfram uses this term to describe distributed local state updates of a global state space. In his particular model, the global state space is a hypergraph, and the state updates are replacements of some local subgraphs with other subgraphs. This happens in parallel in all sorts of places, which is a not-too-surprising generalization of cellular automata.

And that's it. It's not very deep, and nobody outside his sphere of influence uses this term for that purpose.

The thing with Stephen Wolfram is that he invents all those terms, uses them as if they are standard terminology in the field (of physics or computer science) while freely mixing them with _actual_ standard terminology. That goes for "branchial graph", "rurial space", "principle of computational equivalence" and also "multicomputation". He is just diving deeper and deeper into his own buzzwordial space.

Seconded -- I don't have much interest in reading the guy's own writing at this point, but I'll gladly read a concise summary that leaves out all the boasting since I assume there might be some actual "content" buried in there.