Wiktionary
d-notice
n. (context UK now historical English) A defence notice; an official request to news editors not to publish or broadcast items on specified subjects for reasons of national security (replaced in 1993 with the DA-notice).
Usage examples of "d-notice".
This and no less than twenty-seven permutations of equal literary worth had been done to death that very afternoon when Hovis had unexpectedly arrived at the office, slapped a D-notice on the whole thing, declared it sub judice and paraphrased the famous Fleet Street axiom with the words, Publish and be nicked.