Webster's Revised Unabridged Dictionary · 1913

Honeymoon

Honeymoon , noun

1.
The first month after marriage. — Addison
2.
A vacation taken together by a newly married couple, usually including a trip away from home.
3.
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. [figurative]