tautochrone
Also found in: Wikipedia.
tautochrone
(ˈtɔːtəˌkrəʊn)n
a curve upon which a moving object will reach a certain point at the same time through gravity from whichever point it starts
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014