The fact or state of being confined as a prisoner, esp. in solitary confinement. Now rare.

Of persons, a dwelling, etc.: Withdrawn from society or intercourse; shut off from access. separate confinement, the system of confining prisoners…

Any one of a number of chambers in a building, typically intended for or inhabited by a single person. colloquial. In plural (without article)…

In the United Kingdom: a practice formerly carried out in certain children's homes whereby children were punished by being placed in solitary…