TAUTOCHRONES

Noun

tautochrones

plural of tautochrone

Source: Wiktionary

TAUTOCHRONE

Tau"to*chrone, n. Etym: [Gr. tautochrone.] (Math.)

Definition: 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.

Source: Webster’s Unabridged Dictionary 1913 Edition