Lockdown

A lockdown (/ˈlɒkˌdaʊn/ ^ⓘ) is a restriction policy for people, community or a country to stay where they are, usually due to specific risks that could possibly harm the people if they move and interact freely.

The term is used for a prison protocol that usually prevents people, information or objects from leaving an area. The protocol can usually only be initiated by someone in a position of authority.^[1]

A lockdown can also be used to protect people inside a facility or, for example, a computing system, from a threat or other external event. In buildings doors leading outside are usually locked so that no person may enter or exit.