There are several synonyms for the word "ALK" which is short for "alkali". Alkali is a basic substance that has a pH level above seven on the pH scale. Some other terms that can be used instead of alk include base, caustic, and lye. These words are often used in chemistry to describe substances that have a high pH level and can react with acids to form salts. Other similar words to Alk include alkaline, alkalinity, and alkalosis. These words are often used in medical and scientific fields to describe things that are basic or high in pH level.