the confining of prisoners to their cells, as following a riot or other disturbance.
2.
a security measure taken during an emergency to prevent people from leaving or entering a building:
The school remains under lockdown due to police activity in the area.
Origin
1970-75;lock1 + -down, probably extracted from nouns formed from phrasal verbs, such as crackdown, shutdown, etc.
Examples from the web for lockdown
The park will then go into lockdown, and every exit from the park will be closed.
There is an intermediate school nearby that was in lockdown but that has been lifted and parents are getting their kids.
The campus buildings went on lockdown shortly after the officer was shot.
As news of the shooting broke, the campus shifted rapidly into lockdown mode.
The trains aren't running reliably and the streets are in a state of lockdown.
There were metal detectors to enforce this extreme lockdown.
He is held in twenty-three-hour lockdown solitary confinement, and the press is not allowed to interview him.
Between the incidents, the school and the police failed to lockdown the campus.
Hours after police retook control of the plaza, the tiny island nation was in lockdown mode.
Both say that the tribal territory is in lockdown, and that a curfew has been put in place.
British Dictionary definitions for lockdown
lockdown
/ˈlɒkˌdəʊn/
noun
1.
(US) a security measure in which those inside a building such as a prison, school, or hospital are required to remain confined in it for a time: many schools remained under lockdown yesterday
Contemporary definitions for lockdown
noun
the state of being grounded and denied privileges
Usage Note
slang
Word Origin and History for lockdown
n.
also lock-down, from 1940s in various mechanical senses, from lock (v.) + down (adv.). Prison sense is by 1975, American English.
Slang definitions & phrases for lockdown
lockdown
noun
The state of being grounded and denied privileges: can't go to the mall; I'm on lockdown
A relationship in which one is controlled or confined by the other: wanted to go to the party, but his girl's got him in lockdown