Definitions

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun A protocol followed in an emergency that involves confining people in a secure place, such as the confinement of prison inmates in cells after a disturbance, or the locking of students and teachers in classrooms after a violent attack.
  • noun A situation in which this protocol is undertaken.
  • noun A facility, such as a prison, where people considered to be dangerous are locked inside living quarters or otherwise confined.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun The confinement of people in their own rooms (or cells) as a security measure after a disturbance
  • noun US A contrivance to fasten logs together in rafting.

Etymologies

from Wiktionary, Creative Commons Attribution/Share-Alike License

From lock +‎ down

Examples

Comments

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