mer ‧ cu ‧ ri ‧ al /mɜːˈkjʊəriəl $ mɜːrˈkjʊr-/ BrE AmE adjective
1 . literary having feelings that change suddenly and without warning:
an actor noted for his mercurial temperament
2 . literary quick and clever:
her mercurial wit
3 . technical containing mercury