The Collaborative International Dictionary of English v.0.48:

Glum \Glum\, v. i.
   To look sullen; to be of a sour countenance; to be glum.
   [Obs.] --Hawes.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Glum \Glum\ (gl[u^]m), n. [See Gloom.]
   Sullenness. [Obs.] --Skelton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Glum \Glum\, a.
   Moody; silent; sullen.
   [1913 Webster]

         I frighten people by my glun face.       --Thackeray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

glum
    adj 1: moody and melancholic
    2: showing a brooding ill humor; "a dark scowl"; "the
       proverbially dour New England Puritan"; "a glum, hopeless
       shrug"; "he sat in moody silence"; "a morose and unsociable
       manner"; "a saturnine, almost misanthropic young genius"-
       Bruce Bliven; "a sour temper"; "a sullen crowd" [syn: dark,
       dour, glowering, glum, moody, morose, saturnine,
       sour, sullen]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "glum":
   beetle-browed, black, black-browed, brooding, broody, chapfallen,
   close-lipped, crabbed, crestfallen, dark, dejected, depressed,
   dismal, dispirited, doleful, dour, down, dumpish, frowning, gloomy,
   glowering, grim, grum, long-faced, low, lowering, lugubrious,
   melancholy, moodish, moody, mopey, moping, mopish, morose, mumpish,
   oppressed, pessimistic, sad, saturnine, scowling, silent, sour,
   sulky, sullen, surly, taciturn, tight-lipped, woebegone