The Collaborative International Dictionary of English v.0.48:

Quicksilver \Quick"sil`ver\, n. [Quick living + silver; -- so
   called from its fluidity; cf. G. quecksilber, L. argentum
   vivum. See Quick, a.] (Chem.)
   The metal mercury; -- so called from its resemblance to
   liquid silver.
   [1913 Webster]

   Quicksilver horizon, a mercurial artificial horizon. See
      under Horizon.

   Quicksilver water, a solution of mercury nitrate used in
      artificial silvering; quick water.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mercury \Mer"cu*ry\, n. [L. Mercurius; akin to merx wares.]
   1. (Rom. Myth.) A Latin god of commerce and gain; -- treated
      by the poets as identical with the Greek Hermes, messenger
      of the gods, conductor of souls to the lower world, and
      god of eloquence.
      [1913 Webster]

   2. (Chem.) A metallic element mostly obtained by reduction
      from cinnabar, one of its ores. It is a heavy, opaque,
      glistening liquid (commonly called quicksilver), and is
      used in barometers, thermometers, etc. Specific gravity
      13.6. Symbol Hg (Hydrargyrum). Atomic weight 199.8.
      Mercury has a molecule which consists of only one atom. It
      was named by the alchemists after the god Mercury, and
      designated by his symbol, [mercury].
      [1913 Webster]

   Note: Mercury forms alloys, called amalgams, with many
         metals, and is thus used in applying tin foil to the
         backs of mirrors, and in extracting gold and silver
         from their ores. It is poisonous, and is used in
         medicine in the free state as in blue pill, and in its
         compounds as calomel, corrosive sublimate, etc. It is
         the only metal which is liquid at ordinary
         temperatures, and it solidifies at about -39[deg]
         Centigrade to a soft, malleable, ductile metal.
         [1913 Webster]

   3. (Astron.) One of the planets of the solar system, being
      the one nearest the sun, from which its mean distance is
      about 36,000,000 miles. Its period is 88 days, and its
      diameter 3,000 miles.
      [1913 Webster]

   4. A carrier of tidings; a newsboy; a messenger; hence, also,
      a newspaper. --Sir J. Stephen. "The monthly Mercuries."
      --Macaulay.
      [1913 Webster]

   5. Sprightly or mercurial quality; spirit; mutability;
      fickleness. [Obs.]
      [1913 Webster]

            He was so full of mercury that he could not fix long
            in any friendship, or to any design.  --Bp. Burnet.
      [1913 Webster]

   6. (Bot.) A plant (Mercurialis annua), of the Spurge
      family, the leaves of which are sometimes used for
      spinach, in Europe.
      [1913 Webster]

   Note: The name is also applied, in the United States, to
         certain climbing plants, some of which are poisonous to
         the skin, esp. to the Rhus Toxicodendron, or poison
         ivy.
         [1913 Webster]

   Dog's mercury (Bot.), Mercurialis perennis, a perennial
      plant differing from Mercurialis annua by having the
      leaves sessile.

   English mercury (Bot.), a kind of goosefoot formerly used
      as a pot herb; -- called Good King Henry.

   Horn mercury (Min.), a mineral chloride of mercury, having
      a semitranslucent, hornlike appearance.
      [1913 Webster]

WordNet (r) 3.0 (2006):

quicksilver
    adj 1: 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" [syn: erratic,
           fickle, mercurial, quicksilver(a)]
    n 1: a heavy silvery toxic univalent and bivalent metallic
         element; the only metal that is liquid at ordinary
         temperatures [syn: mercury, quicksilver, hydrargyrum,
         Hg, atomic number 80]

Moby Thesaurus II by Grady Ward, 1.0:

126 Moby Thesaurus words for "quicksilver":
   April showers, Proteus, active, activist, activistic, alive,
   animated, antelope, arrow, aureate, blue darter, blue streak,
   bouncing, bouncy, brass, brassy, brazen, breezy, brisk, bronze,
   bronzy, bubbly, cannonball, chameleon, changeable, chipper,
   cloud shapes, copper, coppery, coquettish, courser, cupreous,
   cuprous, dart, eagle, ebullient, effervescent, electricity,
   energetic, express train, faddish, ferrous, ferruginous, fickle,
   flash, flighty, flirtatious, frisky, full of go, full of life,
   full of pep, gazelle, gilt, gold, gold-filled, gold-plated, golden,
   greased lightning, greyhound, hare, inconstant, iron, ironlike,
   jet plane, kaleidoscope, lead, leaden, light, lightning, live,
   lively, mercurial, mercurous, mercury, militant, moon, nickel,
   nickelic, nickeline, peppy, perky, pert, pewter, pewtery, rocket,
   rolling stone, scared rabbit, shifting sands, shot, silver,
   silver-plated, silvery, skittish, smacking, snappy, spanking,
   spirited, sprightly, spry, steel, steely, streak,
   streak of lightning, striped snake, swallow, the weather, thought,
   thunderbolt, tin, tinny, torrent, toying, undependable,
   unpredictable, unreliable, vacillating, versatile, vivacious,
   volatile, water, weather vane, weathercock, wheel of fortune,
   whirligig, wind, zingy



The Free On-line Dictionary of Computing (30 December 2018):

Quicksilver

    A dBASE-like compiler for MS-DOS from
   WordTech.

   (1995-05-11)