Gloom (gloom), n.
Etymology: [AS. glom twilight, from the root of E. glow. See Glow, and cf. Glum, Gloam.]
1. Partial or total darkness; thick shade; obscurity; as, the gloom of a forest, or of midnight.
2. A shady, gloomy, or dark place or grove. Before a gloom of stubborn-shafted oaks. Tennyson .
3. Cloudiness or heaviness of mind; melancholy; aspect of sorrow; low spirits; dullness. A sullen gloom and furious disorder prevailed by fits. Burke.
4. In gunpowder manufacture, the drying oven.
1 more senses
Syn. -- Darkness; dimness; obscurity; heaviness; dullness; depression; melancholy; dejection; sadness. See Darkness.
2 other Webster entries under this spelling
Gloom, v. i. [imp. & p. p. Gloomed; p. pr. & vb. n. Glooming.]
1. To shine or appear obscurely or imperfectly; to glimmer.
2. To become dark or dim; to be or appear dismal, gloomy, or sad; to come to the evening twilight. The black gibbet glooms beside the way. Goldsmith. [This weary day] . . . at last I see it gloom. Spenser.
Gloom, v. t.
1. To render gloomy or dark; to obscure; to darken. A bow window . . . gloomed with limes. Walpole. A black yew gloomed the stagnant air. Tennyson.
2. To fill with gloom; to make sad, dismal, or sullen. Such a mood as that which lately gloomed Your fancy. Tennison. What sorrows gloomed that parting day. Goldsmith.
Shades of meaning
Fernald lists gloom only as an antonym, under light.
He lists it without comment; the entries above explain its neighbors.