"Major domo" is a formal term for the highest-ranking servant in a noble household or estate. If you're looking for a synonym for this term, you might try "steward," which is a person who manages the affairs of a household, estate, or organization. Another option is "butler," which is a male domestic servant who is usually in charge of a household's wine cellar and table service. "Manor steward" or "estate manager" are also similar terms that describe a person who oversees the day-to-day operations of a large property. Overall, there are a variety of words that could be used as a synonym for "major domo," depending on the specific context and tone of the writing or conversation.