alcácernounmasculine/ɐɫkɐˈsɛɾ/rareal·cá·cerPortuguesEnglishEspanolFrancaisDefinitionOld term for a castle or fortress.The alcácer dominated the landscape from the hilltop.The ruins of the ancient alcácer are still visible.syncastlefortresscitadelEtymologyDo árabe al-qaṣr, 'o castelo, a fortaleza'.