'Citadel' definitions:

Definition of 'citadel'

From: WordNet
noun
A stronghold into which people could go for shelter during a battle [syn: bastion, citadel]

Definition of 'Citadel'

From: GCIDE
  • Citadel \Cit"a*del\, n. [F. citadelle, It. citadella, di?. of citt? city, fr. L. civitas. See City.] A fortress in or near a fortified city, commanding the city and fortifications, and intended as a final point of defense. [1913 Webster]
  • Syn. -- Stronghold. See Fortress. [1913 Webster]