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

Due to the region’s mercurial weather, the vessels have remained immaculately preserved in the cold, deep waters. —Nicholas Derenzo, AFAR Media, 16 Sep. 2025

But while the issue appears to have dropped off the agenda of the mercurial US leader, along with his threats to annex Canada and to take over the Panama Canal, many Danes still see it as their most pressing – and worrying – diplomatic challenge. —Matthew Chance, CNN Money, 16 Sep. 2025

Tatis can be mercurial at the plate. —Kevin Acee, San Diego Union-Tribune, 15 Sep. 2025

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

Podcast

Get Word of the Day delivered to your inbox!