A dungeon reached by a trap door, often in one of the castle towers The word comes from French meaning "place of forgetting"
Oubliette Concealed dungeon having a trap door in its ceiling as its only opening, where prisoners were often left to starve to death, sometimes in total darkness
öu·blï·ette´, n [Fr , from oublier, L oblivisci, to forget ] a concealed dungeon with a trap door at the top as its only opening, formerly used for persons condemned to perpetual imprisonment or to perish secretly (Webster's New Universal Unabridged Dictionary)
A dungeon with an opening only at the top, found in some old castles and other strongholds, into which persons condemned to perpetual imprisonment, or to perish secretly, were thrust, or lured to fall