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

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

Mix a small amount of castile soap with lukewarm water. —Louise Parks, Martha Stewart, 5 Feb. 2026

To start, wash these items in a bucket or sink filled with warm water and give them a good scrubbing with a brush and dish soap or Castile soap. —Lauren Landers, Better Homes & Gardens, 2 Feb. 2026

The most popular cleaning methods for a menstrual cup include cleaning it with natural products like baking soda or castile soap, submerging it in a sterilizing solution like the type used for baby bottles or boiling it for five to 10 minutes. —Bestreviews, Mercury News, 7 Jan. 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