The Collaborative International Dictionary of English v.0.48:

Depress \De*press"\, v. t. [imp. & p. p. Depressed; p. pr. &
   vb. n. Depressing.] [L. depressus, p. p. of deprimere; de-
   + premere to press. See Press.]
   1. To press down; to cause to sink; to let fall; to lower;
      as, to depress the muzzle of a gun; to depress the eyes.
      "With lips depressed." --Tennyson.
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   2. To bring down or humble; to abase, as pride.
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   3. To cast a gloom upon; to sadden; as, his spirits were
      depressed.
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   4. To lessen the activity of; to make dull; embarrass, as
      trade, commerce, etc.
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   5. To lessen in price; to cause to decline in value; to
      cheapen; to depreciate.
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   6. (Math.) To reduce (an equation) in a lower degree.
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   To depress the pole (Naut.), to cause the sidereal pole to
      appear lower or nearer the horizon, as by sailing toward
      the equator.

   Syn: To sink; lower; abase; cast down; deject; humble;
        degrade; dispirit; discourage.
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WordNet (r) 3.0 (2006):

depressing
    adj 1: causing sad feelings of gloom and inadequacy; "the
           economic outlook is depressing"; "something cheerless
           about the room"; "a moody and uncheerful person"; "an
           uncheerful place" [syn: depressing, cheerless,
           uncheerful] [ant: cheerful]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "depressing":
   affecting, afflictive, bitter, black, bleak, cheerless,
   comfortless, deplorable, depressant, depressive, discomforting,
   discouraging, disheartening, dismal, dismaying, dispiriting,
   distressful, distressing, dolorific, dolorogenic, dolorous, down,
   dreary, funereal, grievous, joyless, lamentable, melancholic,
   melancholy, mournful, moving, oppressive, painful, pathetic,
   piteous, pitiable, poignant, regrettable, rueful, sad, saddening,
   sharp, somber, sore, sorrowful, touching, triste, uncomfortable,
   woebegone, woeful, wretched