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


  1. A person having mercurial qualities.
  2. A preparation containing mercury.