Čo je unstable? Čo je unstable? Tending strongly to change: unstable weather. Not constant; fluctuating: unstable vital signs. Fickle. Lacking control of one's emotions; marked by unpredictable behavior.Not firmly placed; unsteady: an unstable ladder. Chemistry Decomposing readily.Chemistry Highly or violently reactive.Physics Decaying with relatively short lifetime. Used of subatomic particles.Physics Radioactive.