WordReference Random House Learner's Dictionary of American English © 2020
- of or relating to a disaster:a disastrous earthquake.
failing badly:He gave a disastrous presentation of his proposal.
- causing great distress or injury;
calamitous:The rain and cold proved disastrous to his health.
- [Archaic.]foreboding disaster.
- Middle French desastreux, Italian disastroso. See disaster, -ous