What is "heavy metals"

Heavy \Heav"y\, a. [Compar. Heavier; superl. Heaviest.] [OE. hevi, AS. hefig, fr. hebban to lift, heave; akin to OHG. hebig, hevig, Icel. h["o]figr, h["o]fugr. See Heave.]

1. Heaved or lifted with labor; not light; weighty; ponderous; as, a heavy stone; hence, sometimes, large in extent, quantity, or effects; as, a heavy fall of rain or snow; a heavy failure; heavy business transactions, etc.; often implying strength; as, a heavy barrier; also, difficult to move; as, a heavy draught.

2. Not easy to bear; burdensome; oppressive; hard to endure or accomplish; hence, grievous, afflictive; as, heavy yokes, expenses, undertakings, trials, news, etc.

   The hand of the Lord was heavy upon them of Ashdod.
   --1 Sam. v. 6.

   The king himself hath a heavy reckoning to make.
   --Shak.

   Sent hither to impart the heavy news.
   --Wordsworth.

   Trust him not in matter of heavy consequence.
   --Shak.

3. Laden with that which is weighty; encumbered; burdened; bowed down, either with an actual burden, or with care, grief, pain, disappointment.

   The heavy [sorrowing] nobles all in council were.
   --Chapman.

   A light wife doth make a heavy husband.
   --Shak.

4. Slow; sluggish; inactive; or lifeless, dull, inanimate, stupid; as, a heavy gait, looks, manners, style, and the like; a heavy writer or book.

   Whilst the heavy plowman snores.
   --Shak.

   Of a heavy, dull, degenerate mind.
   --Dryden.

   Neither [is] his ear heavy, that it can not hear.
   --Is. lix. 1.

5. Strong; violent; forcible; as, a heavy sea, storm, cannonade, and the like.

6. Loud; deep; -- said of sound; as, heavy thunder.

   But, hark! that heavy sound breaks in once more.
   --Byron.

7. Dark with clouds, or ready to rain; gloomy; -- said of the sky.

8. Impeding motion; cloggy; clayey; -- said of earth; as, a heavy road, soil, and the like.

9. Not raised or made light; as, heavy bread.

10. Not agreeable to, or suitable for, the stomach; not easily digested; -- said of food.

11. Having much body or strength; -- said of wines, or other liquors.

12. With child; pregnant. [R.] Heavy artillery. (Mil.)

    1. Guns of great weight or large caliber, esp. siege, garrison, and seacoast guns.

    2. Troops which serve heavy guns.

       Heavy cavalry. See under Cavalry.

       Heavy fire (Mil.), a continuous or destructive cannonading, or discharge of small arms.

       Heavy metal (Mil.), large guns carrying balls of a large size; also, large balls for such guns.

       Heavy metals. (Chem.) See under Metal.

       Heavy weight, in wrestling, boxing, etc., a term applied to the heaviest of the classes into which contestants are divided. Cf. Feather weight

    3. , under Feather.

       Note: Heavy is used in composition to form many words which need no special explanation; as, heavy-built, heavy-browed, heavy-gaited, etc.

Metal \Met"al\ (? or ?; 277), n. [F. m['e]tal, L. metallum metal, mine, Gr. ? mine; cf. Gr. ? to search after. Cf. Mettle, Medal.]

1. (Chem.) An elementary substance, as sodium, calcium, or copper, whose oxide or hydroxide has basic rather than acid properties, as contrasted with the nonmetals, or metalloids. No sharp line can be drawn between the metals and nonmetals, and certain elements partake of both acid and basic qualities, as chromium, manganese, bismuth, etc.

   Note: Popularly, the name is applied to certain hard, fusible metals, as gold, silver, copper, iron, tin, lead, zinc, nickel, etc., and also to the mixed metals, or metallic alloys, as brass, bronze, steel, bell metal, etc.

2. Ore from which a metal is derived; -- so called by miners.
   --Raymond.

3. A mine from which ores are taken. [Obs.]

   Slaves . . . and persons condemned to metals.
   --Jer. Taylor.

4. The substance of which anything is made; material; hence, constitutional disposition; character; temper.

   Not till God make men of some other metal than earth.
   --Shak.

5. Courage; spirit; mettle. See Mettle.
   --Shak.

   Note: The allusion is to the temper of the metal of a sword blade.
   --Skeat.

6. The broken stone used in macadamizing roads and ballasting railroads.

7. The effective power or caliber of guns carried by a vessel of war.

8. Glass in a state of fusion.
   --Knight.

9. pl. The rails of a railroad. [Eng.]

   Base metal (Chem.), any one of the metals, as iron, lead, etc., which are readily tarnished or oxidized, in contrast with the noble metals. In general, a metal of small value, as compared with gold or silver.

   Fusible metal (Metal.), a very fusible alloy, usually consisting of bismuth with lead, tin, or cadmium.

   Heavy metals (Chem.), the metallic elements not included in the groups of the alkalies, alkaline earths, or the earths; specifically, the heavy metals, as gold, mercury, platinum, lead, silver, etc.

   Light metals (Chem.), the metallic elements of the alkali and alkaline earth groups, as sodium, lithium, calcium, magnesium, etc.; also, sometimes, the metals of the earths, as aluminium.

   Muntz metal, an alloy for sheathing and other purposes, consisting of about sixty per cent of copper, and forty of zinc. Sometimes a little lead is added. It is named from the inventor.

   Prince's metal (Old Chem.), an alloy resembling brass, consisting of three parts of copper to one of zinc; -- also called Prince Rupert's metal.