From Longman Dictionary of Contemporary Englishhush-hushˌhush-ˈhush / $ ˈ‧ ‧/ adjective informal SECRETvery secret Everything was very hush-hush.► see thesaurus at secret
Examples from the Corpus
hush-hush• The date and location of the operation were very hush-hush.• And this is meant to be hush-hush.• What you two so impertinently called my hush-hush experi-ment.• His death was really hush-hush. It was so covered up that you wondered if it wasn't a suicide.• There was a hush-hush meeting with Eliot and I was to keep out of the way.• Some sort of hush-hush oceanography, probably for oil.• 'The Manhattan Project' was the insiders' name for the hush-hush project.• As a matter of fact it was rather a hush-hush sort of business. 