Precarious, delicate, risky, sensitive; of uncertain outcome (by analogy with a ship in shallow water).
To touch bottom lightly and without damage, as a vessel in motion.
To perform a touch-and-go landing.
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.