ommer block

When a proof-of-work miner finds a valid block, another miner may have published a competing block which is added to the tip of the blockchain first. This valid, but stale, block can be included by newer blocks as ommers and receive a partial block reward. The term "ommer" is the preferred gender-neutral term for the sibling of a parent block, but this is also sometimes referred to as an "uncle". This was common for Ethereum when it was a proof-of-work network. Now that Ethereum uses proof-of-stake, only one block proposer is selected per slot.