Metastable

Definition

• (of a state of equilibrium) stable provided it is subjected to no more than small disturbances. "the amount of supercooling a liquid can accept while remaining in metastable equilibrium is limited"
• (of a substance or particle) theoretically unstable but so long-lived as to be stable for practical purposes. "the occurrence of metastable olivine and deep earthquakes in subducting lithosphere"

Context

Also called a "repeller" by Mandelbrot in his discussion of attractors.