quicksilver

Short definition from Wiktionary

Noun

1. 1
   The metal mercury.
2. 2
   An amalgam of mercury and tin applied to the backs of mirrors, quicksilvering.

Adjective

1. 1
   Unpredictable, erratic or fickle; mercurial.

Verb

1. 1
   To overlay with quicksilver.
2. 2
   To treat with quicksilver.