WordWeb Online

1. Indicating evil intent or suggesting tragic developments
   "his tone became menacing";
   - baleful, forbidding, minacious, minatory, ominous, sinister, threatening

1. Pose a threat to; present a danger to
   "The pollution is menacing the crops";
   - endanger, jeopardize, jeopardise [Brit], threaten, imperil, peril
    
2. Express a threat either by an utterance or a gesture
   "he menaced the bank manager with a stick"
    
3. Act in a threatening manner
   "A menacing person"

See also: alarming

Type of: act, be, behave, do, evince [formal], exist, express, show

Encyclopedia: Menacing