noun
or castile soap (ˈ)ka|stēl, -kaa-, -kai-
( -s )
Usage: often capitalized C
Etymology: from Castile, region of Spain where it was originally made
1. : a fine hard bland soap usually white or cream-colored but sometimes marbled or green that is made from olive oil and sodium hydroxide — called also olive-oil castile soap
2. : any of various hard soaps (as a white neutral toilet soap) made partly from olive oil together with other fats or oils (as coconut oil) or wholly from other fats and oils