< /kɑsˈti lyɑ, -yɑ/. a former kingdom comprising most of Spain.
noun
- a former kingdom comprising most of modern Spain: originally part of León, it became an independent kingdom in the 10th century and united with Aragon (1469), the first step in the formation of the Spanish state
medieval Spanish county and later kingdom, from Vulgar Latin castilla, from Latin castella, plural of castellum “castle, fort, citadel, stronghold” (see castle (n.)); so called in reference to the many fortified places there during the Moorish wars. The name in Spanish is said to date back to c.800. Related: Castilian. As a fine kind of soap, in English from 1610s.