'Guardroom' definitions:

Definition of 'guardroom'

(from WordNet)
noun
A cell in which soldiers who are prisoners are confined
noun
A room used by soldiers on guard

Definition of 'Guardroom'

From: GCIDE
  • Guardroom \Guard"room`\, n. (Mil.) The room occupied by the guard during its term of duty; also, a room where prisoners are confined. [1913 Webster]