秘而不宣
mì'ér​bù​xuān

to keep something secret

  1. 秘 mì verb
    to keep secret
    to keep secret; to withhold from public knowledge; to hide
  2. 而 ér conjunction
    but
    Used to connect ideas that contrast or conflict; yet; but; on the other hand
  3. 不宣 bù​xuān
    not to declare
    (bound form) To not make public; to not publicize or spread; often used in fixed expressions like 心照不宣 xīn​zhào​bù​xuān or 秘而不宣 mì'ér​bù​xuān