That dank, stone-walled underground prison where wretched prisoners were kept manacled in medieval days? That was a dungeon, otherwise known as the "keep," and most familiar to us today from a million video games and movies.

In fact, the original meaning of dungeon was of something overground rather than underground, coming from the Old French term donjon, meaning the "great tower of a castle," and the underground meaning only came later. Rapunzel in the fairy tale was held captive in a tower rather than an underground cell and if she hadn't been, her long hair wouldn't have been much help in her escape.

Definitions of dungeon
  1. noun
    the main tower within the walls of a medieval castle or fortress
    synonyms: donjon, keep
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    Black Hole of Calcutta
    a dungeon (20 feet square) in a fort in Calcutta where as many as 146 English prisoners were held overnight by Siraj-ud-daula; the next morning only 23 were still alive
    type of:
    fastness, stronghold
    a strongly fortified defensive structure
  2. noun
    a dark cell (usually underground) where prisoners can be confined
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    a dungeon with the only entrance or exit being a trap door in the ceiling
    type of:
    cell, jail cell, prison cell
    a room where a prisoner is kept
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