Synonyms of mercurial

mercurial

adjective

(ˌ)mər-ˈkyu̇r-ē-əl 

as in volatile

likely to change frequently, suddenly, or unexpectedly

the boss's mood is so mercurial that we never know how he's going to react to anything

Synonyms & Similar Words

• volatile
• unpredictable
• unstable
• changeful
• inconsistent
• variable
• temperamental
• fickle
• uncertain
• capricious
• mutable
• unsettled
• inconstant
• fluctuating
• changeable
• erratic
• fluid
• skittish
• up in the air
• unsteady
• flickery
• random
• unreliable
• arbitrary
• haphazard
• ambivalent
• scattered
• aimless
• desultory
• shaky
• stray
• protean
• untrustworthy
• slapdash
• hit-or-miss
• undependable
• vacillating
• dicey
• wavering
• versatile
• adaptable
• irregular
• mobile
• shilly-shallying
• hesitating
• shilly-shally

Antonyms & Near Antonyms

• constant
• certain
• stable
• immutable
• steady
• predictable
• stationary
• unchanging
• invariable
• unchangeable
• uniform
• settled
• persistent
• permanent
• even
• unvarying
• changeless
• durable
• equable
• reliable
• lasting
• abiding
• dependable
• true
• trustworthy
• sure
• trusty
• tried
• tried-and-true

Synonym Chooser

How does the adjective mercurial differ from other similar words?

Some common synonyms of mercurial are capricious, fickle, inconstant, and unstable. While all these words mean "lacking firmness or steadiness (as in purpose or devotion)," mercurial implies a rapid changeability in mood.

made anxious by her boss's mercurial temperament

When could capricious be used to replace mercurial?

The words capricious and mercurial can be used in similar contexts, but capricious suggests motivation by sudden whim or fancy and stresses unpredictability.

an utterly capricious critic

When is fickle a more appropriate choice than mercurial?

While in some cases nearly identical to mercurial, fickle suggests unreliability because of perverse changeability and incapacity for steadfastness.

performers discover how fickle fans can be

When is it sensible to use inconstant instead of mercurial?

The synonyms inconstant and mercurial are sometimes interchangeable, but inconstant implies an incapacity for steadiness and an inherent tendency to change.

an inconstant friend

When would unstable be a good substitute for mercurial?

Although the words unstable and mercurial have much in common, 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

Example Sentences

Recent Examples of mercurial

Meanwhile, his mercurial style and public controversies, from social media firestorms to clashes with regulators, have brought volatility to Tesla’s stock and reputation. —Nick Lichtenberg, Fortune, 5 Sep. 2025

The tiniest details take center stage during this time, as this mercurial sign operates at the peak of its celestial expression. —Valerie Mesa, People.com, 2 Sep. 2025

Japan’s contributions to a stable international order are more valuable than ever as the United States becomes increasingly protectionist and mercurial. —Mireya Solís, Foreign Affairs, 1 Sep. 2025

The mercurial chef was a stern taskmaster who demanded the absolute best from everyone who worked for him. —Kori Rumore, Chicago Tribune, 31 Aug. 2025

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