somber

Short definition from Wiktionary

Adjective

1. 1
   Dark; gloomy; shadowy, dimly lit.
2. 2
   Dull or dark in colour or brightness.
3. 3
   Melancholic, gloomy, dreary, dismal; grim.
4. 4
   Grave; extremely serious.

Verb

1. 1
   To make sombre or dark; to make shady.