What does "dark cloud" mean?

A situation or future event that causes worry, problems or unhappiness, likened to such a cloud overhead in the sky.

Dark cloud

Common synonyms include: angry clouds, black cat, black clouds, black magellanic cloud, bright diffuse nebula, broken mirror.

noun

noun ·Rare ·Advanced level

Noun

1
A situation or future event that causes worry, problems or unhappiness, likened to such a cloud overhead in the sky. idiomatic
"Strikes remain the other dark cloud hanging over the railway."

"Strikes remain the other dark cloud hanging over the railway."