The Collaborative International Dictionary of English v.0.48:

Gloom \Gloom\, v. i. [imp. & p. p. Gloomed; p. pr. & vb. n.
   Glooming.]
   1. To shine or appear obscurely or imperfectly; to glimmer.
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   2. To become dark or dim; to be or appear dismal, gloomy, or
      sad; to come to the evening twilight.
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            The black gibbet glooms beside the way. --Goldsmith.
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            [This weary day] . . . at last I see it gloom.
                                                  --Spenser.
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The Collaborative International Dictionary of English v.0.48:

Gloom \Gloom\, v. t.
   1. To render gloomy or dark; to obscure; to darken.
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            A bow window . . . gloomed with limes. --Walpole.
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            A black yew gloomed the stagnant air. --Tennyson.
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   2. To fill with gloom; to make sad, dismal, or sullen.
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            Such a mood as that which lately gloomed
            Your fancy.                           --Tennison.
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            What sorrows gloomed that parting day. --Goldsmith.
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The Collaborative International Dictionary of English v.0.48:

Gloom \Gloom\ (gl[=oo]m), n. [AS. gl[=o]m twilight, from the
   root of E. glow. See Glow, and cf. Glum, Gloam.]
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   1. Partial or total darkness; thick shade; obscurity; as, the
      gloom of a forest, or of midnight.
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   2. A shady, gloomy, or dark place or grove.
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            Before a gloom of stubborn-shafted oaks. --Tennyson
                                                  .
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   3. Cloudiness or heaviness of mind; melancholy; aspect of
      sorrow; low spirits; dullness.
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            A sullen gloom and furious disorder prevailed by
            fits.                                 --Burke.
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   4. In gunpowder manufacture, the drying oven.
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   Syn: Darkness; dimness; obscurity; heaviness; dullness;
        depression; melancholy; dejection; sadness. See
        Darkness.
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WordNet (r) 3.0 (2006):

gloom
    n 1: a state of partial or total darkness; "he struck a match to
         dispel the gloom" [syn: gloom, somberness,
         sombreness]
    2: a feeling of melancholy apprehension [syn: gloom,
       gloominess, somberness, sombreness]
    3: an atmosphere of depression and melancholy; "gloom pervaded
       the office" [syn: gloom, gloominess, glumness]