1. Darkened by clouds
   "a louring sky";
   - heavy, lowering[2], sullen, threatening, loury, lowery

1. Look angry or sullen, wrinkle one's forehead, as if to signal disapproval
   "He lourd at the messenger";
   - frown, glower, lower[2]
    
2. (of weather, sky, or landscape) appear dark and threatening
   "Storm clouds loured on the horizon";
   - lower[2]

See also: cloudy

Type of: grimace, make a face, pull a face [informal]