What is the meaning of Lock_down?

To secure (something); to blockade and lock (a building or campus) so as to prevent ingress or egress; to make (people) stay locked indoors for their safety.

To limit the use of (a computer network) to only users with permission.

To make (an arrangement) secure, definite, or permanent; to fix.

To cause (another person) to enter into an exclusive romantic relationship.

To travel through a flight of locks on a waterway in a downhill direction.

Source: wiktionary.org