Hairpin turn

acute curve (often one of a series) in a road, especially on a steep incline

A hairpin turn (also hairpin bend, hairpin corner, or just hairpin), is a very tight corner. It makes a vehicle turn almost 180° to continue on the road. It gets its name from the way it looks like a hairpin or bobby pin. Hairpin turns may be called switchbacks in American English.

The type of hair pin (bobby pin) from which a 'hairpin turn' takes its name.

Hairpin turns may be built when a road or path climbs up or down a steep slope. This allows the path to travel the slope with a smaller slope. Hairpin turns may be used in race tracks to slow down the race cars after a long, fast straight.