ˈämənəs adjective
Etymology: Latin ominosus, from omin-, omen + -osus -ose
1. : of or relating to an omen : being or exhibiting an omen
the continual wars and revolutions so ominous of the future — Margaret Parton
2. : indicative of future misfortune or calamity : causing anxiety and fear : potentially disastrous
the ominous waves of cloud seemed to advance with terrific speed — O.E.Rölvaag
a dead and ominous silence prevailed everywhere — J.A.Froude
the ominous sounds the motor was making — Herbert Passin
Synonyms:
portentous , fateful , inauspicious , unpropitious : ominous applies to that which shows a menacing, threatening, and frightful character foreshadowing evil or tragic developments, sometimes rather vague
there was something ominous about it, and in intangible ways one was made to feel that the worst was about to come — Jack London
they formed together an ominous cloud charged with forces of uncertain magnitude, but of the reality of which Italy had already terrible experience — J.A.Froude
portentous is now likely to indicate the prodigious, huge, impressive, marvelous, or monstrous, and only secondarily to suggest the character of a portent, a forewarning of calamity to come
in the midst of a portentous silence, the consul unrolled his papers, evidently intending to produce an effect by the exceeding bigness of his looks — Herman Melville
something quivered in every fiber of his being, like moonlit ripples on the sea. He felt at the same time a portentous stillness and an immense enterprise — H.G.Wells
fateful may imply an especial importance, often solemn, decreed by fate; it is often simply a synonym for momentous
the moving, fateful story of his death — H.O.Taylor
the hour seemed awful to them, and the hearts within them burned as though of fateful matters their souls were newly learned — William Morris
six thousand years ago, the Nile, the begetter of water and grain, was as fateful to the fellah as it is today — Mary Lindsay
inauspicious and unpropitious may suggest the presence of distinctly unfavorable signs or may be simply synonyms for unlucky or unfavorable
while my words with inauspicious thunderings shook Heaven — P.B.Shelley
unpropitious weather
an unpropitious attitude for a politician seeking reelection to take