guardhouse

/G AA1 R D HH AW0 S/
noun
  1. 1

    A station for guards, especially at the entrance of a town, castle, etc.

noun
  1. 1

    A prison operated by the military.

Synonyms

Source: https://en.wiktionary.org/wiki/guardhouse, https://en.wiktionary.org/wiki/military%20prison