保守秘密
to not tell people about something
They managed to keep the school's problems quiet for a while. 他们设法把学校的问题保密了一阵子。
You're a qualified skiing instructor? You kept that quiet! 你有滑雪教练资格？你从来没说过！
The company decided to keep the report's findings quiet in case they affected sales.
An attack was imminent, but journalists were told to keep it quiet.
I'm quitting this job on Friday, but keep it quiet,OK?
See also: keep verb (STAY)