[Groxx]

Yea, I think most would lean towards requiring one or both of:

    - it's a distributed consensus system (often around "blocks", but e.g. iota is not)
    - it's a chain of hashes to prevent mutation (around "chains")

And I doubt we'll ever get everyone to agree on what subset (including null) of those are "a blockchain".

Very (very) few things benefit from distributed consensus IMO. And not all altcoins use blocks at all. So I tend to lean towards hash-chains. Publicly-verifiable immutability is useful in quite a lot of real-world scenarios.