n. 1. The first month after marriage. Addison. [ 1913 Webster ]
2. A vacation taken together by a newly married couple, usually including a trip away from home. [ PJC ]
3.Hence: [ fig. ] Any initial period of harmony after two or more people or organizations begin working together; as, the usual honeymoon for a newly elected president was cut short by resumption of partisan sniping over the budget. [ PJC ]