hush up(v.+adv.)
防止…张扬出去，掩盖hide information about a situation because you do not want people to know about it
▲hush sth ⇔ up
He tried to hush up the fact.他试图掩盖事实。

用作不及物动词
▲S+～(+A)
Hush now and try to sleep.别出声了，睡吧。
用作及物动词
▲S+～+n./pron.
The mother hushed her noisy child.那位母亲叫她的孩子安静下来。

A hush fell over the onlookers.旁观者们突然静了下来。