Synonyms for Ominous (same or very similar meaning)
WordNet sense 1 (threatening or foreshadowing evil or tragic developments):
baleful, forbidding, menacing, minacious, minatory, sinister, threatening
WordNet sense 2 (causing alarm or fear):
alarming
WordNet sense 3 (presaging ill fortune):
ill, inauspicious
From the ODE community, based on WordNet
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