Imperfectly illuminated; dismal through obscurity or darkness; dusky; dim; clouded; as, the cavern was gloomy.
source: Webster 1913
adjective satellite
depressingly dark
The gloomy forest. The glooming interior of an old inn. `gloomful' is archaic.
source: WordNet 3.0
filled with melancholy and despondency
Gloomy at the thought of what he had to face. Gloomy predictions. A gloomy silence. Took a grim view of the economy. The darkening mood. Lonely and blue in a strange city. Depressed by the loss of his job. A dispirited and resigned expression on her face. Downcast after his defeat. Feeling discouraged and downhearted.
source: WordNet 3.0
causing dejection
A blue day. The dark days of the war. A week of rainy depressing weather. A disconsolate winter landscape. The first dismal dispiriting days of November. A dark gloomy day. Grim rainy weather.