I never found out what he did; it was all very hush-hush.我从未弄清楚他做的是什么, 一切都秘不示人。

Apparently there's a very hush-hush project under way up north.很显然, 在北面有一个非常秘密的工程正在进行。

They were desperate to keep the marriage hush-hush.他们拼命想要隐瞒这桩婚事。