A curve between two points along which a body can move under gravity in a shorter time than for any other curve. Open English WordNet

In physics and mathematics, a brachistochrone curve, or curve of fastest descent, is the one lying on the plane between a point A and a lower point B, where B is not directly below A, on which a bead slides frictionlessly under the influence of a uniform gravitational field to a given end point in the shortest time. Wikipedia

Fastest descent curve Wikidata