Tau"to*chrone (?), n. [Gr. ?, for ? ?
the same + ? time: cf. F. tautochrone.] (Math.) A
curved line, such that a heavy body, descending along it by the action of
gravity, will always arrive at the lowest point in the same time, wherever
in the curve it may begin to fall; as, an inverted cycloid with its base
horizontal is a tautochrone.