Pronunciation IPA (key): /dəˈmɪnjən/ or /doʊˈmɪnjən/ Audio (US)(file) Hyphenation: do‧min‧ion Noun Singular dominion Plural dominions Power of right of ruling over something. I have dominion over my room. (countable) A dominion is a territory ruled by someone. My sister's iPhone is her dominion. Wikiwand - on Seamless Wikipedia browsing. On steroids.Remove ads