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Webster 1913 Edition

Noun.

A place where persons under arrest are temporarily locked up; a watchhouse; a jail.

See also: lock-up and lock up

lockup ‎(plural lockups)

(slang) A jail cell, or a period of incarceration.
He's in lockup for 30 days for drunk and disorderly.
(Britain, chiefly) A storage unit with a door secured by a padlock or deadbolt; a garage
Joe keeps his other car in a lockup downtown.

prison — see prison