WordNet sense 1 (causing or suggestive of sorrow or gloom):

depressing, depressive, saddening

WordNet sense 2 (experiencing or showing sorrow or unhappiness):

sad

WordNet sense 3 (characterized by hopelessness; filled with gloom):

grim, darkening

WordNet sense 4 (without hope because there seems to be no possibility of comfort or success):

hopeless

WordNet sense 5 (reflecting gloom):

glum, long-faced

WordNet sense 6 (affected or marked by low spirits):

dejected

WordNet sense 7 (causing dejection):

blue, dingy, disconsolate, dismal, drab, drear, dreary, sorry, dispiriting, dingy

WordNet sense 8 (lacking cheer; depressing):

cheerless, uncheerful

WordNet sense 9 (depressingly dark):

sulky, gloomful, glooming

WordNet sense 10 (devoid of or deficient in light or brightness; shadowed or black):

dark