(n.) A dungeon with an opening only at the top, found in some old castles and other strongholds, into which persons condemned to perpetual imprisonment, or to perish secretly, were thrust, or lured to fall.

POW camp black hole borstal borstal institution bridewell brig bucket caboose calaboose can cell chokey concentration camp condemned cell confine constrain death cell death house death row detention camp federal prison forced-labor camp gaol guardhouse hoosegow house of correction house of detention immure incarcerate industrial school intern internment camp jail jailhouse jug keep labor camp lockup maximum-security prison minimum-security prison oubliette pen penal colony penal institution penal settlement penitentiary prison prison camp prisonhouse quod reform school reformatory sponging house state prison stockade the hole tollbooth training school