lock down

verb

1. To secure (something).

   “But even as the fireball races both skywards and downwards, the mortally-wounded Major Francis Harvey, Royal Marines, crawls over to a voicepipe despite the loss of both legs and orders the magazines locked down and flooded. It's his last act on this Earth; his body will be found later, next to the voicepipe.”

2. To secure (something).

   “Police have the area locked down until the situation is all-clear.”

3. To secure (something).
4. To make (an arrangement) secure, definite, or permanent; to fix.
5. To cause (another person) to enter into an exclusive romantic relationship.

   “It took me some time, but I finally locked her down.”

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