The Collaborative International Dictionary of English v.0.48:

Poison \Poi"son\, n. [F. poison, in Old French also, a potion,
   fr. L. potio a drink, draught, potion, a poisonous draught,
   fr. potare to drink. See Potable, and cf. Potion.]
   1. Any agent which, when introduced into the animal organism,
      is capable of producing a morbid, noxious, or deadly
      effect upon it; as, morphine is a deadly poison; the
      poison of pestilential diseases.
      [1913 Webster]

   2. That which taints or destroys moral purity or health; as,
      the poison of evil example; the poison of sin.
      [1913 Webster]

   Poison ash. (Bot.)
      (a) A tree of the genus Amyris (Amyris balsamifera)
          found in the West Indies, from the trunk of which a
          black liquor distills, supposed to have poisonous
          qualities.
      (b) The poison sumac (Rhus venenata). [U. S.]

   Poison dogwood (Bot.), poison sumac.

   Poison fang (Zool.), one of the superior maxillary teeth of
      some species of serpents, which, besides having the cavity
      for the pulp, is either perforated or grooved by a
      longitudinal canal, at the lower end of which the duct of
      the poison gland terminates. See Illust. under Fang.

   Poison gland (Biol.), a gland, in animals or plants, which
      secretes an acrid or venomous matter, that is conveyed
      along an organ capable of inflicting a wound.

   Poison hemlock (Bot.), a poisonous umbelliferous plant
      (Conium maculatum). See Hemlock.

   Poison ivy (Bot.), a poisonous climbing plant (formerly
      Rhus Toxicodendron, or Rhus radicans, now classified
      as Toxicodendron radicans) of North America. It is
      common as a climbing vine, especially found on tree
      trunks, or walls, or as a low, spreading vine or as a
      shrub. As a low vine it grows well in lightly shaded
      areas, recognizable by growing in clusters of three
      leaves. Its leaves are trifoliate, rhombic-ovate, and
      variously notched. Its form varies slightly from location
      to location, leading to some speculation that it may
      consist of more than one species. Many people are poisoned
      by it, though some appear resistant to its effects.
      Touching the leaves may leave a residue of an oil on the
      skin, and if not washed off quickly, sensitive areas of
      skin become reddened and develop multiple small blisters,
      lasting for several days to several weeks, and causing a
      persistent itch. The toxic reaction is due to an oil,
      present in all parts of the plant except the pollen,
      called urushiol, the active component of which is the
      compound pentadecylacatechol (according to [a

      href="http:]/www.jaxmed.com/articles/Diseases/poison_ivy_dermatitis.htm">Charles
      H. Booras). See Poison sumac. It is related to poison
      oak, and is also called mercury.

   Poison nut. (Bot.)
      (a) Nux vomica.
      (b) The tree which yields this seed (Strychnos
          Nuxvomica). It is found on the Malabar and Coromandel
          coasts.

   Poison oak (Bot.), a dermatitis-producing plant often
      lumped together with the poison ivy (Toxicodendron
      radicans) in common terminology, but more properly
      distinguished as the more shrubby Toxicodendron
      quercifolium (syn. Toxicodendron diversilobum), common
      in California and Oregon. Opinion varies as to whether the
      poison oak and poison ivy are only variants of a single
      species. See poison ivy, above.

   Poison sac. (Zool.) Same as Poison gland, above. See
      Illust. under Fang.

   Poison sumac (Bot.), a poisonous shrub formerly considered
      to be of the genus Rhus (Rhus venenata), but now
      classified as Toxicodendron vernix; -- also called
      poison ash, poison dogwood, and poison elder. It has
      pinnate leaves on graceful and slender common petioles,
      and usually grows in swampy places. Both this plant and
      the poison ivy (Toxicodendron radicans, formerly Rhus
      Toxicodendron) have clusters of smooth greenish white
      berries, while the red-fruited species of this genus are
      harmless. The tree (Rhus vernicifera) which yields the
      celebrated Japan lacquer is almost identical with the
      poison sumac, and is also very poisonous. The juice of the
      poison sumac also forms a lacquer similar to that of
      Japan.
      [1913 Webster +PJC]

   Syn: Venom; virus; bane; pest; malignity.

   Usage: Poison, Venom. Poison usually denotes something
          received into the system by the mouth, breath, etc.
          Venom is something discharged from animals and
          received by means of a wound, as by the bite or sting
          of serpents, scorpions, etc. Hence, venom specifically
          implies some malignity of nature or purpose.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mercury \Mer"cu*ry\, v. t.
   To wash with a preparation of mercury. [Obs.] --B. Jonson.
   [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):

mercury
    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]
    2: (Roman mythology) messenger of Jupiter and god of commerce;
       counterpart of Greek Hermes
    3: the smallest planet and the nearest to the sun
    4: temperature measured by a mercury thermometer; "the mercury
       was falling rapidly"

Moby Thesaurus II by Grady Ward, 1.0:

104 Moby Thesaurus words for "Mercury":
   Agdistis, Amor, Aphrodite, Apollo, Apollon, Ares, Artemis, Ate,
   Athena, Bacchus, Ceres, Cora, Cronus, Cupid, Cybele, Demeter,
   Despoina, Diana, Dionysus, Dis, Earth, Eros, Gaea, Gaia, Ge,
   Great Mother, Hades, Helios, Hephaestus, Hera, Here, Hermes,
   Hestia, Hymen, Hyperion, Iris, Jove, Juno, Jupiter, Jupiter Fidius,
   Jupiter Fulgur, Jupiter Optimus Maximus, Jupiter Pluvius,
   Jupiter Tonans, Kore, Kronos, Magna Mater, Mars, Minerva, Mithras,
   Momus, Neptune, Nike, Olympians, Olympic gods, Ops, Orcus,
   Paul Revere, Persephassa, Persephone, Pheidippides, Phoebus,
   Phoebus Apollo, Pluto, Poseidon, Proserpina, Proserpine, Rhea,
   Saturn, Tellus, Uranus, Venus, Vesta, Vulcan, Zeus, asteroid,
   carrier, commercialism, commissionaire, courier,
   diplomatic courier, emissary, estafette, express, go-between,
   industrialism, inferior planet, major planet, mercantilism,
   message-bearer, messenger, minor planet, nuncio, planet, planetoid,
   post, postboy, postrider, runner, secondary planet, solar system,
   superior planet, terrestrial planet, wanderer



Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "mercury":
   April showers, Gyropilot, Proteus, antelope, arrow,
   automatic pilot, blue darter, blue streak, boatheader, boatsteerer,
   cannonball, chameleon, cicerone, cloud shapes, courier, courser,
   cowherd, coxswain, dart, dragoman, drover, eagle, electricity,
   express train, flash, gazelle, glass, goatherd, greased lightning,
   greyhound, guide, guidepost, guider, hare, helmsman, herd,
   herdsman, jet plane, kaleidoscope, light, lightning, moon,
   navigator, pilot, pointer, quicksilver, river pilot, rocket,
   rolling stone, scared rabbit, shepherd, shifting sands, shot,
   steerer, steersman, streak, streak of lightning, striped snake,
   swallow, the weather, thermal detector, thermometer, thermostat,
   thought, thunderbolt, torrent, tour director, tour guide, water,
   weather vane, weathercock, wheel of fortune, whirligig, wind



The Elements (07Nov00):

mercury
Symbol: Hg
Atomic number: 80
Atomic weight: 200.59
Heavy silvery liquid metallic element, belongs to the zinc group. Used
in
thermometers, barometers and other scientific apparatus. Less reactive
than zinc and cadmium, does not displace hydrogen from acids. Forms a
number of complexes and organomercury compounds.