Definition of: alkali

(al′kə·lī) noun plural ·lis or ·lies
1. Chem. A compound of hydrogen and oxygen with any one of the elements lithium, sodium, potassium, rubidium, and cesium, or the ammonium radical, characterized by great solubility in water and capability of neutralizing acids and of turning red litmus paper blue.
2. Anything that will neutralize an acid, as lime, magnesia, etc.
3. Sodium carbonate.
4. Mineral matter, not including sodium chloride, found in natural waters and in soils. [ < MF alcali < Arabic al-qalīy the ashes of saltwort]