hush-hush
/hʌʃˈhʌʃ
/adjective informal
(Especially of an official plan or project) highly secret or confidential: a hush-hush research unit...
- Main is also working on a hush-hush project involving a Scottish-based online games business and a couple of high-profile sports journalists.
- The top-secret project was so hush-hush they were barred from even taking photographs.
- A lot of the game world is top secret and hush-hush.
