Pronunciation: (pri-kâr'ē-us),[key] —adj. 1. dependent on circumstances beyond one's control; uncertain; unstable; insecure: a precarious livelihood. 2. dependent on the will or pleasure of another; liable to be withdrawn or lost at the will of another: He held a precarious tenure under an arbitrary administration. 3. exposed to or involving danger; dangerous; perilous; risky: the precarious life of an underseas diver. 4. having insufficient, little, or no foundation: a precarious assumption.