> What defines a blockchain for you?

A (potentially distributed) datastructure of some kind, which resembles a linked-list, and ensures its integrity using some sort of cryptographic hash of the previous link such that changing any link but the most recent invalidates the whole chain. Literally -- a chain of (data) blocks.

A non-engineering description of a "blockchain" should be considered to be misleading.

edit - also, I'd take cryptocurrencies more seriously if they could stay out of the headlines for a while

Is utterly funny to read people's opinions bashing against blockchain technology and when asked about a simple definition they fail to mention the use of consensus protocols which was, already 10 years ago, the huge innovation that lead to this revolution.

Consensus protocols are nothing new. The novel part of blockchains is the actual blockchain

https://en.wikipedia.org/wiki/Paxos_(computer_science)

You're thinking of a distributed ledger, which combine blockchains with consensus protocols

I prefer the "proof of work != blockchain" comments when people include the most common consensus protocol in their simple description of blockchain.