Definition
Selfish mining is a strategy where a miner (or pool) with significant hashrate secretly mines blocks without broadcasting them. By strategically releasing these hidden blocks, the selfish miner can cause honest miners to waste work on blocks that will be orphaned.
Research has shown that selfish mining can be profitable for miners with as little as 25-33% of network hashrate under certain conditions. However, it has never been conclusively demonstrated at scale on Bitcoin, partly because the strategy carries risk and requires sustained high hashrate.
In Simple Terms
A strategy of withholding mined blocks to gain advantage over honest miners. Theoretical but rarely observed.
A theoretical attack strategy where a miner withholds found blocks to gain an advantage over honest miners, potentially earning more than their fair share of rewards.