(North American hairpin turn)
Pronunciation
noun
A sharp U-shaped bend in a road.
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Riders on the Giro d'Italia and other grand tour races must make effective use of hairpin bends, going both uphill and down.

And a real hairpin, AKA "Bobby Pin", just for fun.

[Grr. Personal gripe. I went to all the trouble of making a fancy, illustration for grimalkin because it had been offered by Lexico...and only then checked to see if it had been used before...of course it had. Seven years has passed and I feel very grumpy, almost spiteful, one might say! Now, I'll need to keep that illustration for some future post...if I remember it.]