noun. a region of central Spain; a former kingdom that comprised most of modern Spain and united with Aragon to form Spain in 1479.
1. Noun, singular or mass Add a couple of tablespoons of castile soap and distilled vinegar to 1 gallon of water and swish it around the inside the barrel. 2. Adjective You can even buy castile soap by the gallon on Amazon and use it for everything from laundry to your cat's bathtime.