castilian/kəˈstɪljən/EtymologyFrom Castile + -ian as a calque of Spanish castellano (“Of or related to Castile, Spain, or the Spanish language”). Doublet of castellano, castellanus, castellan, and chatelain.castilian means of, from, or relating to Castile. Lexicurio rates it Sui generis — a strength score of 85 out of 100.adjOf, from, or relating to Castile.nameThe Castilian dialect of Spanish, often (especially historically) considered the prestige dialect of Spanish.Synonym of Spanish, the language of Spain and its former colonies.nounA native of Castile.