Pronunciation enPR: ălʹkə-lī', IPA (key): /ˈæl.kəˌlaɪ/ Audio (US)(file) Noun Singular alkali Plural alkalis or alkalies (countable & uncountable) (chemistry) An alkali is an aqueous solution with a pH value of more than seven. Antonym: acid soda, potash, and ammonia are examples of alkalis.Wikiwand - on Seamless Wikipedia browsing. On steroids.Remove ads