n. A vacation taken separately by each person in a newly married couple in lieu of a honeymoon.
Also Seen As
Busy lives lead couples to take separate honeymoons. You heard correctly. Some people are actually taking honeymoons without their spouses called "unimoons." … Demanding jobs and conflicting schedules lead to the separate post-wedding trips.
—Larry Dowdy, “How busy is too busy,” Sunny 93.5, January 06, 2015
There's [sic] always going to be new trends in weddings. From a hairstyle ever [sic] bride wants to wear to a type of picture people seem to be taking, every season brings something new. But there is one new trend I just can't even wrap my head around.

They're called uni-moons and they are apparently honeymoons you go on by yourself.
—Nancy Hall, “The Worst Wedding Trend Ever,” Fun 107, January 02, 2015
2014 (earliest)
Even as Melissa and I married, in a small ceremony with family and close friends, our overworking led us to join the disquieting "uni-moon" trend. Instead ofa honeymoon trip together in the busy weeks after our wedding, we each took separate, individual vacations without each other — uni-moons, or what amounted to a few days of free time at the end of separate work trips.
—William Powers, New Slow City, New World Library, October 27, 2014
See this post for the not-so-sweet history of the word honeymoon.