What is "brachystochrone"

Brachystochrone \Bra*chys"to*chrone\, n. [Incorrect for brachistochrone, fr. Gr. bra`chistos shortest (superl. of brachy`s short) + ? time : cf. F. brachistochrone. ] (Math.) 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.

n. (alternative form of brachistochrone English)