What does "ominous" mean?

Ominous: 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. He had a good ominous name to have made a peace. Bacon. In the heathen worship of God, a sacrifice without a heart was accounted ominous. South. -- Om"i*nous*ly, adv. -- Om"i*nous*ness, n.