What does "disastrous" mean?

1. (catastrophic or failing) causing great damage, harm, or very bad results. 2. (unlucky or ill-omened) suggesting that something very bad is going to happen.

Is it correct to say "The weather was disaster for our trip."?

No — say "The weather was disastrous for our trip.". Use the adjective 'disastrous' to describe a noun, rather than the noun 'disaster'.

disastrous

adj.

US //dɪˈzæstɹəs// UK //dˌɪsˈæstɹəs// dis·as·trous

1 catastrophic or failing (adj.)
B2 Upper Intermediate

causing great damage, harm, or very bad results.

resulting in a disaster; characterized by catastrophic failure or significant negative consequences.

Example

The heavy rain had a disastrous effect on the outdoor concert.

Example

The company's decision to ignore the market warnings proved disastrous, leading to a total collapse of their share price within months.
- catastrophic
- calamitous
- devastating
Pitfall

The weather was disaster for our trip.

The weather was disastrous for our trip.

Use the adjective 'disastrous' to describe a noun, rather than the noun 'disaster'.
2 unlucky or ill-omened (adj.)
C2 Proficiency Literary

suggesting that something very bad is going to happen.

portending or foreboding disaster; having the character of an ill omen.

Example

The dark clouds felt like a disastrous sign before the long journey.

Example

In the opening scene of the play, the disastrous alignment of the stars serves as a warning of the tragedy to come.
- ominous
- ill fated
- unlucky
- auspicious
- promising

Origin

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 (ắstron)).