Quantum indeterminacy is the apparent necessary incompleteness in the description of a physical system, that has become one of the characteristics of the standard description of quantum physics.
Prior to quantum physics, it was thought that

(a) a physical system had a determinate state which uniquely determined all the values of its measurable properties, and conversely

(b) the values of its measurable properties uniquely determined the state.

 Albert Einstein may have been the first person to carefully point out the radical effect the new quantum physics would have on our notion of physical state.