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)
Origin: 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.