Cas·til·ian 
(kă-stĭlyən)
(kă-stĭlyən)n.
1.
a. A native or inhabitant of Castile.
b. A person of Castilian ancestry.
2.
a. The Spanish dialect of Castile.
b. The standard literary and official form of Spanish, which is based on this dialect.
adj.
Of or relating to Castile or its people, language, or culture.