Lye (noun)

1. A strong alkaline solution, typically of potassium hydroxide or sodium hydroxide, used in making soap and for washing.
2. A chemical substance used as a cleaning agent, especially in making soap.

Origin:

Old english lēag, of germanic origin; related to dutch loog and german lauge.

Examples:

1. The soap maker used lye to make soap.
2. The workers were handling lye with care to avoid injury.
3. The lye was used to clean the drains.
4. He used lye to make a homemade soap.
5. The process of making soap includes the use of lye and fats.