Having the qualities fabled to belong to the god Mercury; swift; active; sprightly; fickle; volatile; changeable; as, a mercurial youth; a mercurial temperament
relating to or having characteristics (eloquence, shrewdness, swiftness, thievishness) attributed to the god Mercury; "more than Mercurial thievishness"
relating to or containing or caused by mercury; "mercurial preparations"; "mercurial sore mouth" relating to or having characteristics (eloquence, shrewdness, swiftness, thievishness) attributed to the god Mercury; "more than Mercurial thievishness" relating to or under the (astrological) influence of the planet Mercury; "the Mercurial canals