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]

The Collaborative International Dictionary of English v.0.48:

lugubriousness \lu*gu"bri*ous*ness\ n.
   1. excessive sadness and mournfulness.

   Syn: gloominess.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

lugubriousness
    n 1: the quality of excessive mournfulness and uncheerfulness
         [syn: gloominess, lugubriousness, sadness]