Norton's dome

Etymology
Devised by John D. Norton in 2003.

Proper noun

 * 1) A thought experiment that exhibits a nondeterministic system within the bounds of Newtonian mechanics. It involves an idealized particle initially sitting motionless at the apex of an idealized radially symmetrical frictionless dome of a certain form. The particle may, after an arbitrary period of time, slide down the dome in an arbitrary direction, contrary to intuition.