WordWeb Online

1. Showing a brooding ill humour
   "a glowering scowl"
   - dark, dour, glum, moody, morose, saturnine, sour, sullen

1. Look at with a fixed gaze
   "The girl glowered at the man who tried to make a pass at her"
   - glare
    
2. Look angry or sullen, wrinkle one's forehead, as if to signal disapproval
   - frown, lour, lower[2]

See also: gloweringly, ill-natured

Type of: grimace, make a face, pull a face, stare