Gloomy, a. [Compar. Gloomier; superl. Gloomiest.]
1. Imperfectly illuminated; dismal through obscurity or darkness; dusky; dim; clouded; as, the cavern was gloomy. "Though hid in gloomiest shade." Milton.
2. Affected with, or expressing, gloom; melancholy; dejected; as, a gloomy temper or countenance.
Syn. -- Dark; dim; dusky; dismal; cloudy; moody; sullen; morose; melancholy; sad; downcast; depressed; dejected; disheartened.
Shades of meaning
Fernald has no entry of its own for gloomy; he lists it under dark, morose.
Where he writes about it:
Murky is said of that which is at once dark, obscure, and gloomy; as, a murky den; a murky sky. — from dark
Figuratively, dark is emblematic of sadness, agreeing with somber, dismal, gloomy, also of moral evil; as, a dark deed. — from dark