ominous

adjective

1. portending evil or harm; foreboding; threatening; inauspicious: an ominous bank of dark clouds.
2. indicating the nature of a future event, for good or evil; having the significance of an omen; being a portent: Some of these events were immediately ominous, while others only later revealed themselves as such.

adjective

1. foreboding evil
2. serving as or having significance as an omen

adj.1580s, from Latin ominosus “full of foreboding,” from omen (genitive ominis) “foreboding” (see omen). Related: Ominousness.