mercurial

Adjective

• 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
    

• liable to sudden unpredictable change
  • erratic behavior
    
  • fickle weather
    
  • mercurial twists of temperament
    
  • a quicksilver character, cool and willful at one moment, utterly fragile the next
    

Related words

• Synonyms: 
  Mercurial , erratic , fickle , quicksilver(a)