oubliette
/ˌuːbliˈɛt/
noun
- A secret dungeon with an opening only at the top, into which prisoners were dropped and forgotten.
- Legends say the oubliette held prisoners who were never seen again.
- The castle's oubliette was hidden beneath a stone slab in the floor.
- The tour guide showed visitors the dark, narrow oubliette where captives were left to die.