Source : Webster's Revised Unabridged Dictionary (1913)

Gloominess \Gloom"i*ness\, n.
   State of being gloomy. --Addison.

Source : WordNet®

gloominess
     n 1: an atmosphere of depression and melancholy; "gloom pervaded
          the office" [syn: {gloom}, {glumness}]
     2: a feeling of melancholy apprehension [syn: {gloom}, {somberness}]
     3: excessive sadness and mournfulness [syn: {lugubriousness}]