Source : Webster's Revised Unabridged Dictionary (1913)

Iron \I"ron\ ([imac]"[u^]rn), a. [AS. [=i]ren, [=i]sen. See
   {Iron}, n.]
   1. Of, or made of iron; consisting of iron; as, an iron bar,
      dust.

   2. Resembling iron in color; as, iron blackness.

   3. Like iron in hardness, strength, impenetrability, power of
      endurance, insensibility, etc.; as:
      (a) Rude; hard; harsh; severe.

                Iron years of wars and dangers.   --Rowe.

                Jove crushed the nations with an iron rod.
                                                  --Pope.
      (b) Firm; robust; enduring; as, an iron constitution.
      (c) Inflexible; unrelenting; as, an iron will.
      (d) Not to be broken; holding or binding fast; tenacious.
          ``Him death's iron sleep oppressed.'' --Philips.

   Note: Iron is often used in composition, denoting made of
         iron, relating to iron, of or with iron; producing
         iron, etc.; resembling iron, literally or figuratively,
         in some of its properties or characteristics; as,
         iron-shod, iron-sheathed, iron-fisted, iron-framed,
         iron-handed, iron-hearted, iron foundry or
         iron-foundry.

   {Iron age}.
      (a) (Myth.) The age following the golden, silver, and
          bronze ages, and characterized by a general
          degeneration of talent and virtue, and of literary
          excellence. In Roman literature the Iron Age is
          commonly regarded as beginning after the taking of
          Rome by the Goths, A. D. 410.
      (b) (Arch[ae]ol.) That stage in the development of any
          people characterized by the use of iron implements in
          the place of the more cumbrous stone and bronze.

   {Iron cement}, a cement for joints, composed of cast-iron
      borings or filings, sal ammoniac, etc.

   {Iron clay} (Min.), a yellowish clay containing a large
      proportion of an ore of iron.

   {Iron cross}, a Prussian order of military merit; also, the
      decoration of the order.

   {Iron crown}, a golden crown set with jewels, belonging
      originally to the Lombard kings, and indicating the
      dominion of Italy. It was so called from containing a
      circle said to have been forged from one of the nails in
      the cross of Christ.

   {Iron flint} (Min.), an opaque, flintlike, ferruginous
      variety of quartz.

   {Iron founder}, a maker of iron castings.

   {Iron foundry}, the place where iron castings are made.

   {Iron furnace}, a furnace for reducing iron from the ore, or
      for melting iron for castings, etc.; a forge; a
      reverberatory; a bloomery.

   {Iron glance} (Min.), hematite.

   {Iron hat}, a headpiece of iron or steel, shaped like a hat
      with a broad brim, and used as armor during the Middle
      Ages.

   {Iron horse}, a locomotive engine. [Colloq.]

   {Iron liquor}, a solution of an iron salt, used as a mordant
      by dyers.

   {Iron man} (Cotton Manuf.), a name for the self-acting
      spinning mule.

   {Iron} {mold or mould}, a yellow spot on cloth stained by
      rusty iron.

   {Iron ore} (Min.), any native compound of iron from which the
      metal may be profitably extracted. The principal ores are
      magnetite, hematite, siderite, limonite, G["o]thite,
      turgite, and the bog and clay iron ores.

   {Iron pyrites} (Min.), common pyrites, or pyrite. See
      {Pyrites}.

   {Iron sand}, an iron ore in grains, usually the magnetic iron
      ore, formerly used to sand paper after writing.

   {Iron scale}, the thin film which on the surface of wrought
      iron in the process of forging. It consists essentially of
      the magnetic oxide of iron, {Fe3O4>}.

   {Iron works}, a furnace where iron is smelted, or a forge,
      rolling mill, or foundry, where it is made into heavy
      work, such as shafting, rails, cannon, merchant bar, etc.

Source : WordNet®

iron ore
     n : an ore from which iron can be extracted