Colloquially, it often refers to a consensus algorithm paired with a chain of blocks.
Bitcoin’s innovation wasn’t a blockchain, it was a proof-of-work backed consensus algorithm that allowed a group of adversarial peers to agree on the state of a shared blockchain datastructure.
According to the dictionary [1], a blockchain is "a digital database containing information (such as records of financial transactions) that can be simultaneously used and shared within a large decentralized, publicly accessible network"
The distinction here might be with a decentralized network.
"decentralized" isnt necessary to a block chain. However when people say "block chain" in everyday use, they're usually talking about that type. It's a case where the everyday use of a word is different to the actual technical meaning.
Do you have another definition?
Colloquially, it often refers to a consensus algorithm paired with a chain of blocks.
Bitcoin’s innovation wasn’t a blockchain, it was a proof-of-work backed consensus algorithm that allowed a group of adversarial peers to agree on the state of a shared blockchain datastructure.