lock·down /ˈlɒkdaʊn $ ˈlɑːk-/ noun [uncountable and countable]

1. a time when prisoners are not allowed out of their rooms, usually after there has been violence in the prison

2. a time when all the doors in a building are locked in order to protect the people inside from danger:
The school went into lockdown after the shooting.

[TahlilGaran] Dictionary of Contemporary English ▲