official secret 
noun British
A piece of confidential information that is important for national security: it is a crime to disclose an official secret...
- I should like to emphasise with all the power at my command that this case is not primarily about national security or official secrets.
- It is interesting that the attorney general's advice should still be an official secret despite the freedom of information act.
- Apart from extending the protection of official secrets to include any government document, the Bill makes it easier to jail journalists or anyone else found with a leaked government document.
- dose-response curve
- dose–response
- dosh
- dosha
- do-si-do
- dosimeter
- dosimetric
- dosimetry
- do someone a favour
- do someone a good (or bad) turn
- do someone an injustice
- do someone a solid
- do someone credit (or do credit to someone)
- do someone dirt (also do dirt to)
- do someone fine
- do someone good
- do someone in
- do someone no favours
- do someone (or oneself) a mischief
- do someone out of
- do someone over
- do someone proud
- do someone's head in
- do someone/thing a power of good
- do someone/thing down