disaster

catastrophic event

Roots

astro / aster: star
dis- / dif-: apart, away, not, reversal, or disruption

Other words with the astro / aster root

astrology: belief system mapping celestial positions to human affairs
astronaut: space traveler
astronomy: study of celestial objects and space

Disaster once carried the feeling of a bad star overhead: not just trouble, but fate turning dark.

A missed bus was annoying; missing the exam would have been a disaster.

Older usage tied disaster to an unlucky star. The modern word no longer asks you to believe in astrology, but the image still works: the sky seems to have turned against the moment.