The Collaborative International Dictionary of English v.0.48:

Cloud \Cloud\ (kloud), v. t. [imp. & p. p. Clouded; p. pr. &
   vb. n. Clouding.]
   1. To overspread or hide with a cloud or clouds; as, the sky
      is clouded.
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   2. To darken or obscure, as if by hiding or enveloping with a
      cloud; hence, to render gloomy or sullen.
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            One day too late, I fear me, noble lord,
            Hath clouded all thy happy days on earth. --Shak.
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            Be not disheartened, then, nor cloud those looks.
                                                  --Milton.
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            Nothing clouds men's minds and impairs their honesty
            like prejudice.                       --M. Arnold.
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   3. To blacken; to sully; to stain; to tarnish; to damage; --
      esp. used of reputation or character.
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            I would not be a stander-by to hear
            My sovereign mistress clouded so, without
            My present vengeance taken.           --Shak.
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   4. To mark with, or darken in, veins or sports; to variegate
      with colors; as, to cloud yarn.
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            And the nice conduct of a clouded cane. --Pope.
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The Collaborative International Dictionary of English v.0.48:

Clouding \Cloud"ing\, n.
   1. A mottled appearance given to ribbons and silks in the
      process of dyeing.
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   2. A diversity of colors in yarn, recurring at regular
      intervals. --Knight.
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WordNet (r) 3.0 (2006):

clouding
    n 1: the process whereby water particles become visible in the
         sky [syn: clouding, clouding up]