Used in air travel contexts for a planned break in a journey where the passenger leaves the aircraft at an intermediate airport.
I took advantage of a stopover and stayed one night in Singapore.
途中下車 is used for stopping midway on a train or bus journey, while 途中降機 is the equivalent term used specifically for stopovers during air travel.
Compound of 途中 (midway) + 降機 (disembarking from an aircraft).