The "block" in "blockchain" refers to a certain kind of a block. Strictly speaking it refers to the "block" that is defined in the Bitcoin white paper (which itself doesn't mention blockchain): https://bitcoin.org/bitcoin.pdf

Extending from this, "blockchain" may mean any structure that has the same properties as Nakamoto's "blockchain".

Otherwise, the structure is just a hash list, a hash chain or a Merkle tree.