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dependent on the will or pleasure of another; liable to be withdrawn or lost at the will of another: He held a precarious tenure under an arbitrary administration.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.
Origin: 1640–50; < Latin precārius obtained by entreaty or mere favor, hence uncertain. See prayer1
1646, a legal word, "held through the favor of another," from L. precarius "obtained by asking or praying," from prex (gen. precis) "entreaty, prayer." Notion of "dependent on the will of another" led to sense "risky, dangerous, uncertain" (1687).