lockdown
From Longman Dictionary of Contemporary Englishlockdownlock·down /ˈlɒkdaʊn $ ˈlɑːk-/ noun [countable, uncountable] 1 a time when prisoners are not allowed out of their rooms, usually after there has been violence in the prison2 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.