Each week The Sun's John McIntyre presents a relatively obscure but evocative word with which you may not be familiar, another brick to add to the wall of your vocabulary. This week's word: 

OUBLIETTE

House arrest can be relatively pleasant, and these days even penitentiaries provide heat and light. But sometimes those imprisoned wind up in an oubliette, a kind of dungeon in which the only opening is at the top. It is often a pit concealed below a floor by a trapdoor.

The word entered English in the late eighteenth century. It derives from the French verb oublier, "to forget. 

Example: From The Silence of the Lambs: "The oubliette that held her was in the part of the basement directly beneath the kitchen."