Definition of lye in US English:



  • A strongly alkaline solution, especially of potassium hydroxide, used for washing or cleansing.

    • ‘One member created an alternative cement for the concrete floor of our sauna, using fly ash (from coal burning plants, not waste dumps!), citric acid, lye, and borax.’
    • ‘When you mix ten parts oil with one part of methanol and a pinch of lye (the catalyst), the mixture settles out into about ten parts biodiesel and one part glycerine.’
    • ‘I told him about the time that Mother almost burned herself with lye from the soap we were making.’
    • ‘If more alkalinity was needed, then borax, sodium metaborate, sodium carbonate, or even lye were used.’
    • ‘Because soap is made primarily from a caustic blend of boiled animal fat, lye and soda, it is highly alkaline.’
    • ‘Other household items carried by the stores on wheels included washing powder, liniments, salve, and lye used for making soap.’
    • ‘In oven cleaners, lye and sodium hydroxide can burn skin, eyes, and the respiratory tract.’
    • ‘One of the most popular dishes is lutefisk, stockfish softened in a solution of lye.’
    • ‘To make the Biodiesel, we heated the oil, then mixed in a measured solution of methanol and lye.’
    • ‘From the age of 15 or so, I would have my hair straightened with such hair-loving products as lye and perm solution.’
    • ‘The catalyst is usually a base, either lye (which is NaOH) or potassium hydroxide.’
    • ‘It's important to avoid conventional oven cleaners; they contain lye and ammonia, which can damage your respiratory tract if inhaled.’
    • ‘Technically detergents are called ‘Synthetic Detergents’ as they are not made from fats and lye from which soap is made.’
    • ‘Most conventional whitening toothpastes use sodium or potassium hydroxides, also known as lye, which is considered a poison by the Food and Drug Administration.’
    • ‘I set to work scrubbing on my green hair with the strongest lye soap, hoping for positive results.’
    • ‘Make soap using lye (from hardwood ash) and animal fat.’
    • ‘One involves a chemical reaction: Mix the oil with methanol and lye, and you get a stable, vegetable-based fuel called biodiesel.’
    • ‘For example, sodium oxide dissolved in water yields sodium hydroxide, or lye.’
    • ‘Sodium hydroxide, NaOH, also known as lye and caustic soda, is one of the most important of all industrial chemicals.’
    • ‘Chemistry fans take note: lye is also called caustic soda and sodium hydroxide, but most people just call it lye.’


Old English lēag, of Germanic origin: related to Dutch loog, German Lauge, also to lather.