1. Sex between a male and female where the male has sex with and ejaculates in the females belly button
2. Often performed when partners run out of other sexual acts to practice. Hence, the name "honeymooner" because by the time you reach your honeymoon, you'll have to break out the honeymooner.
Things were getting a little stale after 5 days of sex on our vacation, so I broke out the honeymooner.