castile soap Meaning, Definition & Usage

  1. noun a good hard soap made from olive oil and sodium hydroxide

WordNet

Cas"tile soap"
Etymology
From Castile, or Castilia, a province in Spain, from which it originally came.
Definitions
  1. A kind of fine, hard, white or mottled soap, made with olive and soda; also, a soap made in imitation of the above-described soap.

Webster 1913