- IPA: /ʌnˈsteɪbəɫ/
- Having a strong tendency to change.
- Fluctuating; not constant.
- (chemistry) Readily decomposable.
- (physics) Radioactive, especially with a short half-life.
- (having strong tendency to change) labile
- (fluctuating) instable (rare); see also Thesaurus:unsteady
- (fickle) arbitrary, capricious
- (not held or fixed securely and likely to fall over) tottering, unsteady, wobbly; see also Thesaurus:rickety
- French: instable
- German: instabil, labil
- Italian: instabile
- Portuguese: instável
- Russian: неусто́йчивый
- Spanish: inestable
unstable (unstables, present participle unstabling; past and past participle unstabled)
- (transitive) To release (an animal) from a stable.