The Collaborative International Dictionary of English v.0.48:

Mild \Mild\ (m[imac]ld), a. [Compar. Milder; superl.
   Mildest.] [AS. milde; akin to OS. mildi, D. & G. mild, OHG.
   milti, Icel. mildr, Sw. & Dan. mild, Goth. milds; cf. Lith.
   melas dear, Gr. ? gladdening gifts.]
   Gentle; pleasant; kind; soft; bland; clement; hence, moderate
   in degree or quality; -- the opposite of harsh, severe,
   irritating, violent, disagreeable, etc.; -- applied to
   persons and things; as, a mild disposition; a mild eye; a
   mild air; a mild medicine; a mild insanity.
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         The rosy morn resigns her light
         And milder glory to the noon.            --Waller.
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         Adore him as a mild and merciful Being.  --Rogers.
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   Mild steel, or Low steel, steel that has but little
      carbon in it and is not readily hardened.
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   Syn: Soft; gentle; bland; calm; tranquil; soothing; pleasant;
        placid; meek; kind; tender; indulgent; clement;
        mollifying; lenitive; assuasive. See Gentle.
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The Collaborative International Dictionary of English v.0.48:

Steel \Steel\ (st[=e]l), n. [AS. st[=e]l, st[=y]l, st[=y]le;
   akin to D. staal, G. stahl, OHG. stahal, Icel. st[=a]l, Dan.
   staal, Sw. st[*a]l, Old Prussian stakla.]
   1. (Metal) A variety of iron intermediate in composition and
      properties between wrought iron and cast iron (containing
      between one half of one per cent and one and a half per
      cent of carbon), and consisting of an alloy of iron with
      an iron carbide. Steel, unlike wrought iron, can be
      tempered, and retains magnetism. Its malleability
      decreases, and fusibility increases, with an increase in
      carbon.
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   2. An instrument or implement made of steel; as:
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      (a) A weapon, as a sword, dagger, etc. "Brave Macbeth . .
          . with his brandished steel." --Shak.
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                While doubting thus he stood,
                Received the steel bathed in his brother's
                blood.                            --Dryden.
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      (b) An instrument of steel (usually a round rod) for
          sharpening knives.
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      (c) A piece of steel for striking sparks from flint.
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   3. Fig.: Anything of extreme hardness; that which is
      characterized by sternness or rigor. "Heads of steel."
      --Johnson. "Manhood's heart of steel." --Byron.
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   4. (Med.) A chalybeate medicine. --Dunglison.
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   Note: Steel is often used in the formation of compounds,
         generally of obvious meaning; as, steel-clad,
         steel-girt, steel-hearted, steel-plated, steel-pointed,
         etc.
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   Bessemer steel (Metal.) See in the Vocabulary.

   Blister steel. (Metal.) See under Blister.

   Cast steel (Metal.), a fine variety of steel, originally
      made by smelting blister or cementation steel; hence,
      ordinarily, steel of any process of production when
      remelted and cast.

   Chrome steel, Chromium steel (Metal.), a hard, tenacious
      variety containing a little chromium, and somewhat
      resembling tungsten steel.

   Mild steel (Metal.), a kind of steel having a lower
      proportion of carbon than ordinary steel, rendering it
      softer and more malleable.

   Puddled steel (Metal.), a variety of steel produced from
      cast iron by the puddling process.

   Steel duck (Zool.), the goosander, or merganser. [Prov.
      Eng.]

   Steel mill.
      (a) (Firearms) See Wheel lock, under Wheel.
      (b) A mill which has steel grinding surfaces.
      (c) A mill where steel is manufactured.

   Steel trap, a trap for catching wild animals. It consists
      of two iron jaws, which close by means of a powerful steel
      spring when the animal disturbs the catch, or tongue, by
      which they are kept open.

   Steel wine, wine, usually sherry, in which steel filings
      have been placed for a considerable time, -- used as a
      medicine.

   Tincture of steel (Med.), an alcoholic solution of the
      chloride of iron.

   Tungsten steel (Metal.), a variety of steel containing a
      small amount of tungsten, and noted for its tenacity and
      hardness, as well as for its malleability and tempering
      qualities. It is also noted for its magnetic properties.
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WordNet (r) 3.0 (2006):

mild steel
    n 1: steel with less than 0.15% carbon [syn: mild steel, low-
         carbon steel, soft-cast steel]