Unpredictable, erratic or fickle; mercurial.
The metal mercury.
An amalgam of mercury and tin applied to the backs of mirrors, quicksilvering.
To overlay with quicksilver.
To treat with quicksilver.
Not likely; improbable; not to be reasonably expected.
Not holding out a prospect of success; likely to fail; unpromising.
Something or somebody considered unlikely.
In an improbable manner.