/ˈlɒkˌdəʊn/
an official order to control the movement of people or vehicles because of a dangerous situation （对人或交通工具的）活动限制，行动限制
a three-day lockdown of American airspace
美国为期三天的领空关闭
Prisoners have been placed on lockdown to prevent further violence at the jail.
已对囚犯实行活动限制，以免狱中再出现暴力行为。