Cas-tĭl'ian, n.
(käs-tĭl'yan), n. [Sp. Castellano, from Castilla, N. Lat. Castilia, Castella, Castile, which received this name from the castles or fortresses that were erected on the frontiers as a barrier against the Moors; whence also this province took a castle for its arms.]
Sense 1. An inhabitant or native of Castile, in Spain.
Sense 2. The Spanish language as spoken in Castile.