unstable

play
adjective un·sta·ble \ˌən-ˈstā-bəl\

Definition of unstable

  1. :  not stable :  not firm or fixed :  not constant: such asa :  not steady in action or movement :  irregular an unstable pulseb :  wavering in purpose or intent :  vacillatingc :  lacking steadiness :  apt to move, sway, or fall an unstable towerd (1) :  liable to change or alteration an unstable economy unstable weather (2) :  readily changing (as by decomposing) in chemical or physical composition or in biological activitye :  characterized by lack of emotional control

unstableness

noun

unstably

play \ˌən-ˈstā-b(ə-)lē\ adverb

Examples of unstable in a Sentence

  1. an unstable nuclear reactor core

  2. the minute we put the books down on the unstable desk, the whole stack went crashing to the floor

Recent Examples of unstable from the Web

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'unstable'. Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

13th Century

First Known Use of unstable

13th century

Synonym Discussion of unstable

inconstant, fickle, capricious, mercurial, unstable mean lacking firmness or steadiness (as in purpose or devotion). inconstant implies an incapacity for steadiness and an inherent tendency to change. an inconstant friend fickle suggests unreliability because of perverse changeability and incapacity for steadfastness. performers discover how fickle fans can be capricious suggests motivation by sudden whim or fancy and stresses unpredictability. an utterly capricious critic mercurial implies a rapid changeability in mood. made anxious by her boss's mercurial temperament unstable implies an incapacity for remaining in a fixed position or steady course and applies especially to a lack of emotional balance. too unstable to hold a job

UNSTABLE Defined for English Language Learners

unstable

play
adjective

Definition of unstable for English Language Learners

  • : likely to change

  • : not emotionally or mentally healthy

  • : not held in a secure position : likely to move or fall


UNSTABLE Defined for Kids

unstable

play
adjective un·sta·ble \ˌən-ˈstā-bəl\

Definition of unstable for Students

  1. :  not stable an unstable boat


Medical Dictionary

unstable

play
adjective un·sta·ble \-ˈstā-bəl\

Medical Definition of unstable

  1. :  not stable: asa:  characterized by frequent or unpredictable changes a patient in unstable conditionb:  readily changing (as by decomposing) in chemical composition or biological activity unstable compoundsc:  characterized by lack of emotional control or stability



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