The Collaborative International Dictionary of English v.0.48:

Lugubrious \Lu*gu"bri*ous\, a. [L. lugubris, fr. lugere to
   mourn; cf. Gr. lygro`s sad, Skr. ruj to break.]
   Mournful; indicating sorrow, often ridiculously or feignedly;
   doleful; woful; pitiable; as, a whining tone and a lugubrious
   look.
   [1913 Webster]

         Crossbones, scythes, hourglasses, and other lugubrious
         emblems of mortality.                    --Hawthorne.
   -- Lu*gu"bri*ous*ly, adv. -- Lu*gu"bri*ous*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lugubrious
    adj 1: excessively mournful

Moby Thesaurus II by Grady Ward, 1.0:

38 Moby Thesaurus words for "lugubrious":
   aggrieved, anguished, black, bleak, careworn, cheerless,
   depressant, depressing, dismal, dispiriting, doleful, dolorous,
   dour, dreary, dumb with grief, glum, grief-stricken, griefful,
   grieved, grievous, in grief, joyless, lamentable, morose, mournful,
   oppressive, plaintive, plangent, plunged in grief, rueful,
   saturnine, somber, sorrowed, sorrowful, sorrowing, sullen, tearful,
   woeful