the meaning of "lock down"

[kjc0123]

What is the meaning of "lock down" in the following sentences?

"All hands on the bridge are going to go ahead and get on their knees except for the essential personnel. We're going to lock down the bridge and provide security for the pilot."

[andy hughes]

'Lock down' in this sense means to preventaccess to or from the bridge - probably by locking the door or hatch that is used to go in and out of the bridge, providing, as advised, security.

[Peter Pedant]

Hi KAy jay

You're reading all the right books these days, but if you were to watch trashy American tee-vee programmes set in prisons, then when they all riot, shoot each other etc., someone slams the red button and screams, Lock down!

All more guards rush in, with batons, machine guns, bazookas....and so on

In this case, they are going to lock down the pilot in the bridge (and make him work, I suppose)

There's another related word, lock up, which means incarcerate, put in prison.