"Overnight layover" refers to a situation when a traveler has to stay overnight at a location while waiting for their connecting flight to their final destination. Full definition
I had the opportunity to visit Singapore for two 12 - Hour overnight layovers in Changi Airport on my way to visit family in the Philippines for the holidays. (adventureswithnienie.com)
I was looking at booking the Serenediva Colombo Transit Hotel since we have a 10 hour overnight layover. (pointsmilesandmore.com)
The award chart indicates Business Class availability for the flight home, but this is hardly a practical option: the «best» flight with availability has a 9 hours 40 minutes overnight layover in Munich, boosting the total travel time to more than 24 hours. (pointsaway.com)