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

The Babylon Bee posted a satirical video suggesting that if a female president was mercurial — launching foreign wars, trade wars and petty feuds — and focusing on gewgaws and shoes, she’d be endlessly belittled. — Maureen Dowd, Mercury News, 23 June 2026

Last year, Marisa Abela won a BAFTA for her central role, and now all eyes are on fellow original star Myha’la, who got her biggest showcase yet in season four as the mercurial, brilliant, self-destructive Harper Stern. — David Canfield, HollywoodReporter, 19 June 2026

On cue, left-wing French politicians have already shaken their fists at the prospect of wining and dining the mercurial American leader on French taxpayers’ bill, according to Le Figaro. — Devorah Lauter, ARTnews.com, 17 June 2026

No one else, Netanyahu’s campaign implied, could deliver the mercurial man in the White House. — Yair Rosenberg, The Atlantic, 17 June 2026

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