1 shadowy, shaded, shady, murky, dim, dusky, dull, dark, cloudy, overcast, obscure, black, inky, Literary Stygian:
It is too gloomy a day to have a picnic.
2 depressed, melancholy, sad, dejected, morose, glum, lugubrious, unhappy, cheerless, dismal, moody, down, downcast, desolate, doleful, sorrowful, crestfallen, chap-fallen, downhearted, forlorn, despondent, miserable, joyless, dispirited, despairing, dreary, sullen, blue, distressed, down in the mouth, in the doldrums, saturnine, Colloq (down) in the dumps:
Both of them have been very gloomy since the divorce.
3 depressing, cheerless, dreary, dismal, dispiriting, sad, disheartening:
The décor is much too gloomy for a doctor's waiting-room.