gloom

Short definition from Wiktionary

Noun

1. 1
   Darkness, dimness, or obscurity.
2. 2
   A depressing, despondent, or melancholic atmosphere.
3. 3
   Cloudiness or heaviness of mind; melancholy; aspect of sorrow; low spirits; dullness.
4. 4
   A drying oven used in gunpowder manufacture.

Verb

1. 1
   To be dark or gloomy.
2. 2
   To look or feel sad, sullen or despondent.
3. 3
   To render gloomy or dark; to obscure; to darken.
4. 4
   To fill with gloom; to make sad, dismal, or sullen.
5. 5
   To shine or appear obscurely or imperfectly; to glimmer.