An interesting question Sally, and one I have seen threads on here about before.
Having tried and seen many different approaches to this, my approach is to seek to make any definition of Holacracy relevant to the context I am in. There are many different ways to define and describe Holacracy (replacing hierarchy, evolution, distributing authority, purposeful organisation, processing tensions to effect change...) , and different definitions will be more relevant to different people in different contexts. So I try to get a sense of where someone is and what their interests may be before offering a definition that I sense might fit best for them.
So I think your approach of collecting ideas of how to define it is a good one and I’d love to see a collectively sourced 'Repository of Definitions of Holacracy'.