ominous

threatening or foreshadowing evil or tragic developments

Of or pertaining to an omen or to omens; being or exhibiting an omen; significant; portentous; -- formerly used both in a favorable and unfavorable sense; now chiefly in the latter; foreboding or foreshowing evil; inauspicious; as, an ominous dread.

Latin 'auspicium' meaning omen

“He decided that it meant something, and something ominous--but what?”

— George Meredith, Complete Project Gutenberg Works of George Meredith

“The relief was immediately hidden by tarpaulins to conceal the accident and avoid any undesired ominous interpretations.”