definition of
quicksilver

[1] #1 quicksilver s. [erratic, fickle, mercurial] 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". wn

[2] #2 quicksilver n. [mercury, hydrargyrum, Hg, atomic number 80] a heavy silvery toxic univalent and bivalent metallic element; the only metal that is liquid at ordinary temperatures. wn