mercurial
- 1Changing suddenly and unpredictably in mood or behavior; also, lively and quick-witted.
Her mercurial temperament made her a thrilling performer and a difficult colleague.
The team's mercurial striker can win a match on his own or disappear for weeks.
UsageCan praise (quick, lively) or criticize (unpredictable); often with temperament, mood or wit.
Similarunpredictable, fickle
Oppositestable, steady, placid
Note
The everyday sense, and it cuts both ways. Quick-witted and animated lean toward praise; fickle and unpredictable lean toward complaint, and the same person can be both, as a brilliant but erratic performer is. Its regular partners are temperament, wit and mood, and it has been used of brisk, restless natures since the 1600s.
Checked 31 Oct 2026 · 1 fact
- The temperament sense has been used since the seventeenth century. en.wiktionary.org
- 2Relating to, containing, or caused by the element mercury.
Many hospitals have replaced mercurial thermometers with digital ones.
Workers in the old mine breathed mercurial vapors for years without protection.
Note
Older medical and scientific writing used it for anything made with quicksilver, from the mercurial lotions that John Woodall's The Surgions Mate (1617) warns are dangerous to the mercurial thermometer John Richardson described in 1828 for measuring solar radiation. It usually stands before its noun and does not take more or most.
Checked 3 Nov 2026 · 4 facts
- Older medical and scientific writing used mercurial for things containing mercury or quicksilver. en.wiktionary.org
- John Woodall wrote The Surgions Mate, first published in 1617. en.wikipedia.org
- Woodall warns that mercurial lotions are dangerous. archive.org
- John Richardson described a mercurial thermometer in an 1828 publication about measuring solar radiation. en.wiktionary.org
- 3Relating to the astrological influence of the planet Mercury, or having the traits of a person born under that influence.
Her astrologer insists that the child's chart shows a mercurial nature, drawn to books and learning.
The almanac warned that the week's mercurial influences would bring confusing letters and news.
Note
The astrologer's adjective, and the bridge to the lively, changeable meaning. Joseph Blagrave's 1682 text says the Sun in Mercury's terms inclines a person to be studious, fond of reading and cheerful in work; once the stars dropped out of the picture, the temperament stayed. Zadkiel's 1835 abridgment of William Lilly still calls scholars or divines mercurial men.
Checked 3 Nov 2026 · 5 facts
- The temperament meaning developed from the astrological association with Mercury and survived independently of that belief. readingroo.ms
- Joseph Blagrave's Introduction to Astrology was published in 1682. en.wikipedia.org
- Blagrave says the Sun directed to Mercury's terms inclines the native to study, reading, and cheerfulness in following a calling. en.wiktionary.org
- The description of temperament remained after its astrological explanation was forgotten. readingroo.ms
- Zadkiel's 1835 abridgment of William Lilly calls scholars or divines mercurial men. archive.org
Less common meanings
- 4Relating to Mercury, the Roman god of commerce, gain, communication, and thieves, among other things; by extension, money-making or crafty.
I know the ſhape of's Legge: this is his Hand: / His Foote Mercuriall: his martiall Thigh / The brawnes of Hercules: but his Iouiall face— / Murther in heaven?
1611, William Shakespeare, “The Tragedie of Cymbeline”Near-synonym: Hermesian
Note
In its mythological use the word belongs to the god himself, alongside martial and jovial, the adjectives of his fellow gods. In Shakespeare's Cymbeline, Imogen praises "his foot Mercurial, his Martial thigh," and "his Jovial face." John Quincy Adams could still praise, in 1843, the mercurial wand of commerce, the god's own emblem of trade.
Checked 31 Oct 2026 · 7 facts
- The mythological adjective refers to the Roman god Mercury. en.wiktionary.org
- Martial is an adjective associated with Mars. en.wiktionary.org
- Jovial is an adjective associated with Jove or Jupiter. en.wiktionary.org
- The adjectives occur in Imogen's speech in Act IV, scene ii, but the supplied sequence silently omits 'The brawns of Hercules; but'. folger.edu
- John Quincy Adams used 'the mercurial wand of commerce' in 1843. en.wiktionary.org
- The quoted phrase occurs in Adams's praise of Franklin's diplomatic achievements. en.wiktionary.org
- Mercury's wand, the caduceus, is his emblem and is associated with his role in trade. en.wikipedia.org
- 5Relating to the planet Mercury.
- 6A person born under the influence of the planet Mercury, or, by extension, someone eloquent, quick-witted, furtive, or volatile in character.
- 7A chemical compound containing mercury, including drugs of this kind once used to treat syphilis.
- 8Any of the plants called mercury, especially annual mercury, also known as French mercury (Mercurialis annua).
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Origin
From Latin mercuriālis, 'of Mercury', from Mercurius, the Roman god. The changeable sense comes from the old astrological belief that people born under the planet Mercury were quick and volatile.
Checked 1 Nov 2026 · 2 facts
- Mercurial derives from Latin mercuriālis, meaning 'of Mercury', formed from Mercurius, the Roman god's name. en.wiktionary.org
- The character sense developed from the astrological belief that people born under Mercury were quick and volatile. en.wiktionary.org