The Collaborative International Dictionary of English v.0.48:

Cheerless \Cheer"less\, a.
   Without joy, gladness, or comfort. -- Cheer"less*ly, adv.
   -- Cheer"less*ness, n.
   [1913 Webster]

         My cheerful day is turned to cheerless night.
                                                  --Spenser.

   Syn: Gloomy; sad; comfortless; dispiriting; disconsolate;
        dejected; melancholy; forlorn.
        [1913 Webster]

WordNet (r) 3.0 (2006):

cheerless
    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:

89 Moby Thesaurus words for "cheerless":
   affecting, afflictive, affording no hope, anguished, anxious,
   apathetic, bitter, bleak, bored, comfortless, deplorable,
   depressed, depressing, depressive, despairing, desperate,
   despondent, discomforting, disconsolate, discontented, disgusted,
   dismal, dismaying, dispiriting, distressful, distressing,
   dolorific, dolorogenic, dolorous, dreary, forlorn, funereal,
   grievous, grim, hopeless, humorless, in bad humor, in despair,
   infestive, joyless, lamentable, mirthless, miserable, mournful,
   moving, nauseated, nauseous, oppressive, out of humor,
   out of sorts, painful, pathetic, piteous, pitiable, pleasureless,
   poignant, prey to malaise, regrettable, repelled, revolted, rueful,
   sad, saddening, sharp, sickened, somber, sore, sorrowful, sorry,
   sorryish, suffering angst, touching, uncheerful, uncheery,
   uncomfortable, uneasy, unfulfilled, ungratified, unhappy,
   unhopeful, unjoyful, unmirthful, unquiet, unsatisfied, unsmiling,
   without hope, woebegone, woeful, wretched