adjective

dark or poorly lit, especially so as to appear depressing or frightening.

a gloomy corridor badly lit by oil lamps

dark,ill-lit,poorly lit,shadowy,sunless,dim,sombre,dingy,frowzy,drab,dismal,dreary,murky,depressing,unwelcoming,uninviting,cheerless,joyless,comfortless,funereal,grey,leaden,overcast,cloudy,crepuscular,tenebrous,Stygian,Tartarean,caliginous,subfusc