Depending on the will or pleasure of another; held by courtesy; liable to be changed or lost at the pleasure of another; as, precarious privileges.
source: Webster 1913
adjective satellite
affording no ease or reassurance
A precarious truce.
source: WordNet 3.0
fraught with danger
Dangerous waters. A parlous journey on stormy seas. A perilous voyage across the Atlantic in a small boat. The precarious life of an undersea diver. Dangerous surgery followed by a touch-and-go recovery.