Chatham House Rule
A meeting, or part of a meeting, can be held under the Chatham House Rule.
Under the Rule, participants are free to use the information received, but neither the identity nor the affiliation of the speaker, nor that of any other participant, may be revealed outside the meeting.
The purpose of the Rule is to provide anonymity to speakers who need or want it, while encouraging open discussion and the sharing of information.
Sometimes known - not strictly correctly - as 'Chatham House Rules'.