metastable

形容词 metastable:

1. (of physical systems) continuing in its present state of equilibrium unless sufficiently disturbed to pass to a more stable state of equilibrium

met.a.sta.ble

adj.（形容词）
Of, relating to, or being a relatively unstable and transient but significant state of a chemical or physical system, as of a supersaturated solution or an excited atom.
亚稳的，准稳的：属于、关于或作为一个化学或物理体系的一个相对不稳定、短暂但重要的状态的，如一过饱和溶剂的或一活跃原子的

【引伸】
met.astabil.ity