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The Roman god Mercury was the messenger and herald of the gods and also the god of merchants and thieves (his counterpart in Greek mythology is Hermes). His swiftness inspired the Romans to give his name to what they correctly assessed as the fastest-moving planet in the solar system. Mercury’s speed also apparently made the name apt for English speakers wishing to describe those whose moods travel quickly between extremes, a meaning mercurial has had since the mid-17th century. The adjective mercurial comes from the Latin mercurialis, meaning “of or relating to Mercury.”
Examples of mercurial in a Sentence
Adam Nicolson, God's Secretaries, 2003
Though you could see all three places in one day, each of them makes you want to stay or to keep returning to watch the effects of the changing weather and the mercurial Sicilian light.
—Francine Prose, Atlantic, December 2002
Some scientists suggest that because manic-depressive patients are ever riding the bio-chemical express between emotional extremes, their brains end up more complexly wired and remain more persistently plastic than do the brains of less mercurial sorts.
—Natalie Angier, New York Times, 12 Oct. 1993
Still grinning, still miming, he samba-ed across the floor … and started in on the dishes with a vigor that would have prostrated his mercurial cousin.
—T. Coraghessan Boyle, Harper's, October 1987
the boss's mood is so mercurial that we never know how he's going to react to anything
Holly Ellyatt, CNBC, 16 June 2025
In light of the neighborhood’s status as one of the priciest places in California, and with high-end eateries like Nobu and Buona Fortuna within walking distance, Woody’s has stayed afloat all these years without succumbing to tonier tastes or the whims of the mercurial espresso martini sect.
—Brock Keeling, Oc Register, 29 May 2025
Trump is famously mercurial and transactional, loyal only to his own self-interest.
—Yair Rosenberg, The Atlantic, 22 May 2025
It’s been there since the 1800s and former Leeds stars played on it as kids, including the uniquely mercurial David Batty.
—Phil Hay, New York Times, 22 May 2025
See All Example Sentences for mercurial
Cite this Entry
“Mercurial.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mercurial. Accessed 25 Jun. 2025.
Copy CitationMedical Definition
mercurial
1 of 2 adjective
mercurial
2 of 2 noun
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