reverse curve

Noun

reverse curve (plural reverse curves)

1. A curve to the left or right which immediately curves in the opposite direction, and which is basically S-shaped.
   • One driver told him that a fireman who did not know the route might easily go "over the side" between Corby and Harringworth, unless warned beforehand of the reverse curves; he himself, in his firing days, used to try so to plan his firing that it was unnecessary to add any more coal while passing...1945 July and August, “Notes and News: "A Nice Day's Work"”, in Railway Magazine, page 235
   • Chambers's Technical Dictionary defines a reverse curve as "a curve composed of two arcs, of the same or different radii, with their centres on opposite sides of the curve." In other words, a reverse curve is an "S" curve.1947 September and October, “The Why and The Wherefore: Definition of a Reverse Curve”, in Railway Magazine, page 334