a. [ 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. [ 1913 Webster ]

A mercurial man
Who fluttered over all things like a fan. Byron. [ 1913 Webster ]

2. Having the form or image of Mercury; -- applied to ancient guideposts. [ Obs. ] Chillingworth. [ 1913 Webster ]

3. Of or pertaining to Mercury as the god of trade; hence, money-making; crafty. [ 1913 Webster ]

The mercurial wand of commerce. J. Q. Adams. [ 1913 Webster ]

4. Of or pertaining to, or containing, mercury; as, mercurial preparations, barometer. See Mercury, 2. [ 1913 Webster ]

5. (Med.) Caused by the use of mercury; as, mercurial sore mouth. [ 1913 Webster ]

n. 1. A person having mercurial qualities. Bacon. [ 1913 Webster ]

2. (Med.) A preparation containing mercury. [ 1913 Webster ]

n. [ Mercurial + -ism. ] (Med.) The syndrome produced by poisoning due to exposure to mercury, it fumes, or its compounds; mercury poisoning. Such exposure may occur in mining or smelting, or in using mercurial compounds. [ 1913 Webster ]

n. 1. One under the influence of Mercury; one resembling Mercury in character. [ 1913 Webster ]

2. (Med.) A physician who uses much mercury, in any of its forms, in his practice. [ 1913 Webster ]

v. t. [ imp. & p. p. Mercurialized p. pr. & vb. n. Mercurializing ] 1. (Med.) To affect with mercury. [ 1913 Webster ]

2. (Photography) To treat with mercury; to expose to the vapor of mercury. [ 1913 Webster ]

v. i. To be sprightly, fantastic, or capricious. [ Obs. ] [ 1913 Webster ]

adv. In a mercurial manner. [ 1913 Webster ]