Source : Webster's Revised Unabridged Dictionary (1913)

Dungeon \Dun"geon\, v. t.
   To shut up in a dungeon. --Bp. Hall.

Dungeon \Dun"geon\, n. [OE. donjoun highest tower of a castle,
   tower, prison, F. donjon tower or platform in the midst of a
   castle, turret, or closet on the top of a house, a keep of a
   castle, LL. domnio, the same word as LL. dominus lord. See
   {Dame}, {Don}, and cf. {Dominion}, {Domain}, {Demesne},
   {Danger}, {Donjon}.]
   A close, dark prison, common?, under ground, as if the lower
   apartments of the donjon or keep of a castle, these being
   used as prisons.

         Down with him even into the deep dungeon. -- Tyndale.

         Year after year he lay patiently in a dungeon. --
                                                  Macaulay.

Source : WordNet®

dungeon
     n 1: the main tower within the walls of a medieval castle or
          fortress [syn: {keep}, {donjon}]
     2: a dark cell (usually underground) where prisoners can be
        confined

Source : Free On-Line Dictionary of Computing

Dungeon
     
        {Zork}