Meaning : Threatening or foreshadowing evil or tragic developments.
Example :
A baleful look.
Forbidding thunderclouds.
His tone became menacing.
Ominous rumblings of discontent.
Sinister storm clouds.
A sinister smile.
His threatening behavior.
Ugly black clouds.
The situation became ugly.
Synonyms : baleful, forbidding, menacing, minacious, minatory, ominous, sinister