any of various soluble chemical bases, esp a hydroxide or carbonate of an alkali metal, that combine with acids to form salts: compare acid2, base1 (7)
a soluble chemical salt that is present in some soils of dry regions and prevents the growth of crops
alkalize verb
Middle English via medieval Latin from Arabic al-qili the ashes of the plant saltwort. Alkalis were first obtained from the ashes of various plants, including saltwort