The Collaborative International Dictionary of English v.0.48:

Mars \Mars\ (m[aum]rz), prop. n. [L. Mars, gen. Martis, archaic
   Mavors, gen. Mavortis.]
   1. (Rom. Myth.) The god of war and husbandry.
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   2. (Astron.) One of the planets of the solar system, the
      fourth in order from the sun, or the next beyond the
      earth, having a diameter of about 4,200 miles, a period of
      687 days, and a mean distance of 141,000,000 miles. It is
      conspicuous for the redness of its light.
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   3. (Alchemy) The metallic element iron, the symbol of which
      [male] was the same as that of the planet Mars. [Archaic]
      --Chaucer.
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   Mars brown, a bright, somewhat yellowish, brown.
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