the quality or state of being unstable; lack of stability or firmness.
the tendency to behave in an unpredictable, changeable, or erratic manner: emotional instability.

Origin of instability

1375–1425; late Middle English instabilite < Latin instabilitās. See in-3, stability Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for instability

Contemporary Examples of instability

Historical Examples of instability

  • He knew that both Ruth and he had the instability as well as the initiative of the vagabond.

    The Trail of the Hawk

    Sinclair Lewis

  • The instability of the laws has always been one of the most serious grievances.

  • But alas and alackaday for the instability of youthful affection!

  • When the storm commenced, her dwelling had begun to show symptoms of instability.

    The Red Man's Revenge

    R.M. Ballantyne

  • But in the background of her mind there had always lurked a warning of his instability.


    S. R. Crockett

British Dictionary definitions for instability


noun plural -ties

lack of stability or steadiness
tendency to variable or unpredictable behaviour
physics a fast growing disturbance or wave in a plasma
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for instability

early 15c., from Middle French instabilite "inconstancy," from Latin instabilitatem (nominative instabilitas) "unsteadiness," from instabilis "unsteady," from in- "not, opposite of" (see in- (1)) + stabilis (see stable (2)).

Online Etymology Dictionary, © 2010 Douglas Harper