MERCURIAL

erratic, fickle, mercurial, quicksilver

(adjective) liable to sudden unpredictable change; “erratic behavior”; “fickle weather”; “mercurial twists of temperament”; “a quicksilver character, cool and willful at one moment, utterly fragile the next”

mercurial

(adjective) relating to or containing or caused by mercury; “mercurial preparations”; “mercurial sore mouth”

Mercurial

(adjective) relating to or having characteristics (eloquence, shrewdness, swiftness, thievishness) attributed to the god Mercury; “more than Mercurial thievishness”

Mercurial

(adjective) relating to or under the (astrological) influence of the planet Mercury; “the Mercurial canals”

Source: WordNet® 3.1

Etymology

Noun

mercurial (plural mercurials)

(obsolete) Any of the plants known as mercury, especially the annual mercury or French mercury (Mercurialis annua). [13th–17th c.]

(astrology) A person born under the influence of the planet Mercury; hence, a person having an animated, lively, quick-witted or volatile character. [from 16th c.]

(chemistry) A chemical compound containing mercury.

(pharmacology, historical) A preparation of mercury, especially as a treatment for syphilis. [from 17th c.]

Adjective

mercurial (comparative more mercurial, superlative most mercurial)

(comparable) Having a lively or volatile character; animated, changeable, quick-witted. [from 17th c.]

Synonyms: fickle, unpredictable

(not comparable, astrology) Pertaining to the astrological influence of the planet Mercury; having the characteristics of a person under such influence (see adjective sense 1). [from 16th c.]

(not comparable, astronomy) Pertaining to the planet Mercury. [from 14th c.]

(not comparable, chemistry) Of or pertaining to the element mercury or quicksilver; containing mercury. [from 16th c.]

(not comparable, medicine) Caused by the action of mercury or a mercury compound.

(not comparable, Roman mythology) Pertaining to Mercury, the Roman god of, among other things, commerce, financial gain, communication, and thieves and trickery; hence (comparable), money-making; crafty. [from 15th c.]

Notes

Source: Wiktionary

Mer*cu"ri*al, a. Etym: [L. mercurialis, fr. Mercurius Mercury: cf. F. mercuriel.]

1. Having the qualities fabled to belong to the god Mercury; swift; active; sprightly; fickle; volatile; changeable; as, a mercurial youth; a mercurial temperament. A mercurial man Who fluttered over all things like a fan. Byron.

2. Having the form or image of Mercury; -- applied to ancient guideposts. [Obs.] Chillingworth.

3. Of or pertaining to Mercury as the god of trade; hence, money- making; crafty. The mercurial wand of commerce. J. Q. Adams.

4. Of or pertaining to, or containing, mercury; as, mercurial preparations, barometer. See Mercury, 2.

5. (Med.)

Definition: Caused by the use of mercury; as, mercurial sore mouth.

Mer*cu"ri*al, n.

1. A person having mercurial qualities. Bacon.

2. (Med.)

Definition: A preparation containing mercury.

Source: Webster’s Unabridged Dictionary 1913 Edition