switchback

A railway track on a steep slope in a zigzag formation, in which a train travels in a reverse direction at each switch.

"Of course," said Harry, "there will have to be a branch track built, and a ‘switch-back’ up the hill."

Marriage was the switchback, the giant racer, the lobster teas, the guarantee that one would never be alone.

A railway track on which there are steep ascents and descents, a train moving partially or fully by the force of gravity using the momentum generated when descending to travel up an ascending part of the track; especially (British, dated),

The WR faction claims that the Westbury route is better adapted to high speed, to which advocates of the SR route are apt to retort that the effect of modern diesel traction on schedules over the Salisbury–Exeter switchback has yet to be measured (the speed potential between Waterloo and Salisbury is scarcely disputable) […]

A flight path consisting of a series of steep ascents and descents, generally flown as a stunt.

A path or road having a series of steep ascents and descents.

The switchback road to Diabaig - pronounced 'Jer-vague' - passes through some of the most exhilarating scenery in Scotland. […] With a final swoop, the road plummets down into Diabaig, where cottages are dotted across the slopes of a rocky semi-circle.

A sharp bend in a path or road which causes a traveller to almost reverse their direction of travel, especially one of a series of such bends on an incline; a hairpin bend; also a path or road having such a series of bends.

Already, we enter some airport bathrooms through a brief switchback of walls, so that we don’t ever grasp a door handle.

To take a zigzag course or path.

I climbed 6,683-foot Velka Svistovka, not the highest mountain in the Tatras but arguably the one with the best view. I started from Zelene pleso chata (pleso means "lake" and chata means "hut" in Slovak), and right after turning the first corner I started switchbacking.