Brachystochrone

Bra·chys·to·chrone

Brachystochrone

n.
  1. A curve, in which a body, starting from a given point, and descending solely by the force of gravity, will reach another given point in a shorter time than it could by any other path. This curve of quickest descent, as it is sometimes called, is, in a vacuum, the same as the cycloid. (Math.)