ominous

ominous adjective adverse, alarming, augurial, baleful, bodeful, dangerous, dark, depressing, dire, disastrous, dismaying, dispiriting, disquieting, disturbing, divinatory, fatidic, fatidical, fear-inspiring, fearful, forbidding, forboding, frightful, gloomy, grim, hapless, haunting, ill-boding, ill-fated, ill-omened, ill-starred, inauspicious, luckless, menacing, minacious, minatory, monitory, morbid, perilous, pessimistic, portending evil, portentous, precursive, precursory, premonitory, presageful, presaging, presentient, pythonic, sinister, somber, threatening, threatful, unfortunate, unlucky, unpromising, unpropitious, vatic, vaticinal

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See also: aleatory, bleak, dangerous, dire, imminent, inauspicious, insalubrious, oracular, pending, portentous, presageful, prophetic, suggestive, unfavorable, unpropitious