A dark horse

Dark \Dark\ (d[aum]rk), a. [OE. dark, derk, deork, AS. dearc,
   deorc; cf. Gael. & Ir. dorch, dorcha, dark, black, dusky.]
   1. Destitute, or partially destitute, of light; not
      receiving, reflecting, or radiating light; wholly or
      partially black, or of some deep shade of color; not
      light-colored; as, a dark room; a dark day; dark cloth;
      dark paint; a dark complexion.
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            O dark, dark, dark, amid the blaze of noon,
            Irrecoverably dark, total eclipse
            Without all hope of day!              --Milton.
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            In the dark and silent grave.         --Sir W.
                                                  Raleigh.
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   2. Not clear to the understanding; not easily seen through;
      obscure; mysterious; hidden.
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            The dark problems of existence.       --Shairp.
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            What may seem dark at the first, will afterward be
            found more plain.                     --Hooker.
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            What's your dark meaning, mouse, of this light word?
                                                  --Shak.
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   3. Destitute of knowledge and culture; in moral or
      intellectual darkness; unrefined; ignorant.
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            The age wherein he lived was dark, but he
            Could not want light who taught the world to see.
                                                  --Denhan.
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            The tenth century used to be reckoned by medi[ae]val
            historians as the darkest part of this intellectual
            night.                                --Hallam.
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   4. Evincing black or foul traits of character; vile; wicked;
      atrocious; as, a dark villain; a dark deed.
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            Left him at large to his own dark designs. --Milton.
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   5. Foreboding evil; gloomy; jealous; suspicious.
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            More dark and dark our woes.          --Shak.
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            A deep melancholy took possesion of him, and gave a
            dark tinge to all his views of human nature.
                                                  --Macaulay.
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            There is, in every true woman-s heart, a spark of
            heavenly fire, which beams and blazes in the dark
            hour of adversity.                    --W. Irving.
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   6. Deprived of sight; blind. [Obs.]
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            He was, I think, at this time quite dark, and so had
            been for some years.                  --Evelyn.
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   Note: Dark is sometimes used to qualify another adjective;
         as, dark blue, dark green, and sometimes it forms the
         first part of a compound; as, dark-haired, dark-eyed,
         dark-colored, dark-seated, dark-working.
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   {A dark horse}, in racing or politics, a horse or a candidate
      whose chances of success are not known, and whose
      capabilities have not been made the subject of general
      comment or of wagers. [Colloq.]

   {Dark house}, {Dark room}, a house or room in which madmen
      were confined. [Obs.] --Shak.

   {Dark lantern}. See {Lantern}. -- The

   {Dark Ages}, a period of stagnation and obscurity in
      literature and art, lasting, according to Hallam, nearly
      1000 years, from about 500 to about 1500 A. D.. See
      {Middle Ages}, under {Middle}.

   {The Dark and Bloody Ground}, a phrase applied to the State
      of Kentucky, and said to be the significance of its name,
      in allusion to the frequent wars that were waged there
      between Indians.

   {The dark day}, a day (May 19, 1780) when a remarkable and
      unexplained darkness extended over all New England.

   {To keep dark}, to reveal nothing. [Low]
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