donjon

plural donjons

1. The fortified tower and main residence of a motte or early castle; a keep.

   ‘Start bearding one of these barons in his own castle and next thing you’re being bounced down to the donjon keep.’

   1936, Norman Lindsay, The Flyaway Highway, Sydney: Angus and Robertson, page 85

   2 more examples

   It was a fortress of no great size, consisting of a donjon, or large and high square tower, surrounded by buildings of inferior height, which were encircled by an inner court-yard.

   1819 December 20 (indicated as 1820), Walter Scott, chapter VII, in Ivanhoe; a Romance. […], volume II, Edinburgh: […] Archibald Constable and Co.; London: Hurst, Robinson, and Co. […], →OCLC, page 106

   […] the prison fortress called Qomr, a mound of yellowish brick rising up from the left back of the turbid river, in whose donjon by long tradition the warlord was obliged to lay his head.

   2007, Michael Chabon, Gentlemen of the Road, Sceptre, published 2008, page 132