The Collaborative International Dictionary
Instable \In*sta"ble\, a. [L. instabilis: cf. F. instable. See In- not, and Stable, a., and cf. Unstable.] Not stable; not standing fast or firm; unstable; prone to change or recede from a purpose; mutable; inconstant.
Douglas Harper's Etymology Dictionary
a. Exhibiting instability; unstable
Usage examples of "instable".
The distance of the former and the cautious, unassuming character of it's minister here is one cause of delays: a greater one is the greediness and instable character of the emperor.