However, depending on the context, you could consider using:
* "a due": This is a phrase meaning "owed," which could be used in a situation where someone is leaving and something is owed to them.
* "a do": This is a slang term for a party or event, which could be used in a humorous or informal context when someone is leaving.
It's important to note that these alternatives do not have the same meaning or connotation as "adieu." "Adieu" is a formal farewell, while "a due" and "a do" are more casual and specific to particular situations.