castile soap

noun

cas·​tile soap (ˌ)ka-ˈstēl- 

variants often Castile soap

: a fine hard bland soap made from olive oil and sodium hydroxide

also : any of various similar soaps

Examples of castile soap in a Sentence

Recent Examples on the Web

Mix one drop of castile soap with 16 ounces of warm water in a spray bottle. —Madeline Buiano, Martha Stewart, 18 June 2026

Because Castile soap has a naturally high pH, this soap is probably not going to be the best choice for delicate materials like wool and silk where a detergent with neutral pH levels is recommended. —Patricia Shannon, Southern Living, 31 May 2026

Next, stir in the liquid Castile soap and the remaining water. —Ryan Brennan may 13, Kansas City Star, 13 May 2026

Lemon juice can similarly be too acidic, baking soda can scuff vinyl floors when used in excess, and even Castile soap leaves behind a sticky residue that attracts grime. —Shagun Khare, The Spruce, 8 Mar. 2026

Word History

Etymology

Middle English castell sope, from Castell Castile

First Known Use

15th century, in the meaning defined above

Rhymes for castile soap

• electroscope
• heliotrope
• kaleidoscope
• laryngoscope
• ophthalmoscope
• oscilloscope
• polariscope
• stereoscope
• antelope
• bronchoscope
• cantaloupe
• cystoscope

Medical Definition

castile soap

noun

cas·​tile soap (ˌ)kas-ˌtēl- 

: a fine hard bland soap made from olive oil and sodium hydroxide

also : any of various similar soaps