Source : Webster's Revised Unabridged Dictionary (1913)

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.