lockdown
/ˈlɒkdaʊn/noun
1- N. Amer.the confining of prisoners to their cells, typically in order to regain control during a riot〈北美〉（尤指在监狱暴动期间对囚犯的）防范禁闭。
1.1
- a state of isolation or restricted access instituted as a security measure（作为安全措施的）隔离, 封闭：
the university is on lockdown and nobody has been able to leave.
这所大学目前处于隔离状态, 任何人都无法离开。