Inconvertibly is a word which means something that cannot be converted, changed, or altered in any way. There are many synonyms for this word, including irrevocably, unalterably, and immutably. Other possible synonyms are permanently, irreversibly, and unchangeably. These words suggest a sense of finality and permanence, indicating that once something is inconvertibly defined or set, there is no turning back or alteration to it. So, if you want to express the idea of something being unchangeable, there are many synonyms to choose from that can help you convey this meaning more effectively.