Definition of mercurial

• a. - Having the qualities fabled to belong to the god Mercury; swift; active; sprightly; fickle; volatile; changeable; as, a mercurial youth; a mercurial temperament.
• a. - Having the form or image of Mercury; -- applied to ancient guideposts.
• a. - Of or pertaining to Mercury as the god of trade; hence, money-making; crafty.
• a. - Of or pertaining to, or containing, mercury; as, mercurial preparations, barometer. See Mercury, 2.
• a. - Caused by the use of mercury; as, mercurial sore mouth.
• n. - A person having mercurial qualities.
• n. - A preparation containing mercury.