Mercurial

1. adjective

   relating to or having characteristics (eloquence, shrewdness, swiftness, thievishness) attributed to the god Mercury

   “more than Mercurial thievishness”

2. adjective

   relating to or under the (astrological) influence of the planet Mercury

   “the Mercurial canals”

3. adjective

   relating to or containing or caused by mercury

   “mercurial preparations”

4. adjective

   liable to sudden unpredictable change

   “erratic behavior”

   Similar: erratic, fickle, quicksilver