Disastrous means bringing ruin or very great harm. A disastrous decision, disastrous results, disastrously wrong.
It is stronger than bad and is easily overused, which weakens it. Buried in it is astrum, a star: a disaster was originally an ill-starred event, from the belief that the stars decided fortunes.
1adjectivedisastrousBringing ruin or very great harm.
“The flood had disastrous effects on the farms along the river.”
disastrous is a quality.
From disaster, from Italian disastro — dis, ill, plus astro, a star. A disaster was an ill-starred event.
Italian
disastro
Middle French
desastreux
English, today
disastrous
Built from
From disaster + ous, after Middle French desastreux (modern French désastreux; from desastre (modern French désastre, disaster; from des- + astre, a calque of Italian disastro) + -eux), itself after Italian disastroso, from disastro + -oso, from dis- (“away, without”) (from Latin dis-) + astro (“star, planet”) (from Latin astrum (“star, celestial body”), from Ancient Greek ᾰ̓́στρον).
Etymology from Wiktionary, CC BY-SA