tautochrone

Etymology
From +.

Noun

 * 1)  A curve, 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.
 * An inverted cycloid with its base horizontal is a tautochrone.
 * An inverted cycloid with its base horizontal is a tautochrone.

Adjective

 * 1) tautochronous