Mer·cu·ry n.
 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.
 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,  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° Centigrade to a soft, malleable, ductile metal.
 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.
 4. A carrier of tidings; a newsboy; a messenger; hence, also, a newspaper. --Sir J. Stephen. “The monthly Mercuries.” --Macaulay.
 5. Sprightly or mercurial quality; spirit; mutability; fickleness. [Obs.]
    He was so full of mercury that he could not fix long in any friendship, or to any design.   --Bp. Burnet.
 6. Bot. A plant (Mercurialis annua), of the Spurge family, the leaves of which are sometimes used for spinach, in Europe.
 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.
 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.

From: Webster's Revised Unabridged Dictionary (1913)

 Horn n.
 1. A hard, projecting, and usually pointed organ, growing upon the heads of certain animals, esp. of the ruminants, as cattle, goats, and the like. The hollow horns of the Ox family consist externally of true horn, and are never shed.
 2. The antler of a deer, which is of bone throughout, and annually shed and renewed.
 3. Zool. Any natural projection or excrescence from an animal, resembling or thought to resemble a horn in substance or form; esp.: (a) A projection from the beak of a bird, as in the hornbill. (b) A tuft of feathers on the head of a bird, as in the horned owl. (c) A hornlike projection from the head or thorax of an insect, or the head of a reptile, or fish. (d) A sharp spine in front of the fins of a fish, as in the horned pout.
 4. Bot. An incurved, tapering and pointed appendage found in the flowers of the milkweed (Asclepias).
 5. Something made of a horn, or in resemblance of a horn; as: (a) A wind instrument of music; originally, one made of a horn (of an ox or a ram); now applied to various elaborately wrought instruments of brass or other metal, resembling a horn in shape. “Wind his horn under the castle wall.”  --Spenser. See French horn, under French. (b) A drinking cup, or beaker, as having been originally made of the horns of cattle. “Horns of mead and ale.” --Mason. (c) The cornucopia, or horn of plenty. See Cornucopia. “Fruits and flowers from Amalthæa's horn.” --Milton. (d) A vessel made of a horn; esp., one designed for containing powder; anciently, a small vessel for carrying liquids. “Samuel took the hornof oil and anointed him [David].” --1 Sam. xvi. 13. (e) The pointed beak of an anvil. (f) The high pommel of a saddle; also, either of the projections on a lady's saddle for supporting the leg. (g) Arch. The Ionic volute. (h) Naut. The outer end of a crosstree; also, one of the projections forming the jaws of a gaff, boom, etc. (i) Carp. A curved projection on the fore part of a plane. (j) One of the projections at the four corners of the Jewish altar of burnt offering.  “Joab . . . caught hold on the horns of the altar.” --1 Kings ii. 28.
 6. One of the curved ends of a crescent; esp., an extremity or cusp of the moon when crescent-shaped.
 The moon
 Wears a wan circle round her blunted horns.   --Thomson.
 7. Mil. The curving extremity of the wing of an army or of a squadron drawn up in a crescentlike form.
 Sharpening in mooned horns
 Their phalanx.   --Milton.
 8. The tough, fibrous material of which true horns are composed, being, in the Ox family, chiefly albuminous, with some phosphate of lime; also, any similar substance, as that which forms the hoof crust of horses, sheep, and cattle; as, a spoon of horn.
 9. Script. A symbol of strength, power, glory, exaltation, or pride.
    The Lord is . . . the horn of my salvation.   --Ps. xviii. 2.
 10. An emblem of a cuckold; -- used chiefly in the plural. “Thicker than a cuckold's horn.”
 Horn block, the frame or pedestal in which a railway car axle box slides up and down; -- also called horn plate.
 Horn of a dilemma. See under Dilemma.
 Horn distemper, a disease of cattle, affecting the internal substance of the horn.
 Horn drum, a wheel with long curved scoops, for raising water.
 Horn lead Chem., chloride of lead.
 Horn maker, a maker of cuckolds. [Obs.] --Shak.
 Horn mercury. Min. Same as Horn quicksilver (below).
 Horn poppy Bot., a plant allied to the poppy (Glaucium luteum), found on the sandy shores of Great Britain and Virginia; -- called also horned poppy. --Gray.
 Horn pox Med., abortive smallpox with an eruption like that of chicken pox.
 Horn quicksilver Min., native calomel, or bichloride of mercury.
 Horn shell Zool., any long, sharp, spiral, gastropod shell, of the genus Cerithium, and allied genera.
 Horn silver Min., cerargyrite.
 Horn slate, a gray, siliceous stone.
 To pull in one's horns, To haul in one's horns, to withdraw some arrogant pretension; to cease a demand or withdraw an assertion. [Colloq.]
 To raise the horn, or To lift the horn Script., to exalt one's self; to act arrogantly. “'Gainst them that raised thee dost thou lift thy horn?” --Milton.
 To take a horn, to take a drink of intoxicating liquor. [Low]