Definition from Wiktionary, the free dictionary
- Of or pertaining to an omen or to omens; being or exhibiting an omen; significant.
- Specifically, giving indication of a coming ill; being an evil omen; threatening; portentous; inauspicious.
- California poll support for Jerry Brown's tax increases has ominous implications for U.S. taxpayers too Los Angeles Times Headline April 25, 2011
- 2012 April 29, Nathan Rabin, “TV: Review: THE SIMPSONS (CLASSIC): “Treehouse of Horror III” (season 4, episode 5; originally aired 10/29/1992)”:
- The idea of a merchant selling both totems of pure evil and frozen yogurt (he calls it frogurt!) is amusing in itself, as is the idea that frogurt could be cursed, but it’s really the Shopkeeper’s quicksilver shift from ominous doomsaying to chipper salesmanship that sells the sequence.
Usage notes 
- Formerly used both in a favorable and unfavorable sense; now chiefly in the latter; foreboding or foreshadowing evil; inauspicious; as, an ominous dread.
- Nouns to which "ominous" is often applied: sign, silence, warning, cloud, note, sound, shadow, threat, music, tone, implication, message, presence, development, voice, portent, turn, sky, figure, dream, event, trend, change, day, beginning, growl, cry, signal, pattern.
Derived terms 
Related terms 
of or pertaining to an omen or to omens; being or exhibiting an omen
giving indication of a coming ill
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