Mechanically unreliable or in disrepair.
A mechanical device, particularly an automobile, that is worn out, run down, or mechanically unreliable as indicated by noises it makes in operation.
Unpredictable.
Readily decomposable.
Not stable.
Radioactive, especially with a short half-life.
Fickle.
Having a strong tendency to change.
Fluctuating; not constant.
To release (an animal) from a stable.