Risk management
A deliberate, recorded decision to live with a risk instead of spending more to reduce it.
Formal
The risk treatment option in which the organisation knowingly keeps a risk, because it is within the risk appetite or further controls would cost more than the harm; the decision is made and signed by someone with the authority to own the risk.
In plain English
Like driving on with a small chip at the edge of the windscreen - you note it, decide a new glass is not worth it yet, and look at it again after the winter.
In practice
At a ferry company, the IT manager writes down that the test server has no backup, the director signs that this is acceptable for one year, and the item is put on the list for review.
Why it matters
Accepting a risk is fine; ignoring it is not - the written decision shows who owns it and stops risks from being accepted without anyone deciding.