Orphan Block (Stale Block)

An orphan block is a valid block that is not part of the canonical blockchain due to being produced later or propagating slower than the ultimately adopted valid block.

Orphan blocks are much more common on networks with shorter block times, as it is more likely for multiple Block Producers to produce blocks and submit them to the network within a narrow time frame leading to the acceptance of only a single valid block and the rejection of the others.