In terms of a selfish attack many sources speak of orphaned blocks, i.e. blocks that are not on the main chain and thus not paying any coinbase transaction to its miner. Still I'm not sure and confused by terminology.
Don't we actually mean stale blocks when talking in context of selfish mining?
Despite an answer by Pieter Wuille to a similar question I'm not sure which type would apply to a block outside the best chain in a selfish mining scenario.
Here's an extract to Pieter's answer:
However, there also exist real orphan blocks, with orphan in its original meaning of "having no parent". These are blocks received by a node that does not have its entire ancestry (yet) and thus cannot be validated. Nodes keep such blocks in memory, while asking their peers to fill in the gap of their history. The client does not show these, so when people talk about orphan blocks, they are most likely referring to extinct blocks. Note that since Bitcoin Core v0.10, there are no such orphan blocks anymore, due to a significant change in the download mechanism.
Furthermore I'd love to know if and which of stale or orphaned blocks are pruned from history? And in what time intervals, if so?