Webster's Revised Unabridged Dictionary · 1913

Mercurial

Mercurial , adjective

[Latin mercurialis, from Mercurius Mercury: compare French 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. [Obsolete] — 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.
(Medicine) Caused by the use of mercury; as, mercurial sore mouth.

Mercurial , noun

1.
A person having mercurial qualities. — Bacon
2.
(Medicine) A preparation containing mercury.