Changeable.
Quick to change one’s opinion or allegiance; insincere; not loyal or reliable.
To puzzle, perplex, nonplus.
To deceive, flatter.
Having a strong tendency to change.
Readily decomposable.
Not stable.
Radioactive, especially with a short half-life.
Unpredictable.
Fickle.
Fluctuating; not constant.
To release (an animal) from a stable.