Adjective disastrous has 1 sense
- black, calamitous, disastrous, fatal, fateful - (of events) having extremely unfortunate or dire consequences; bringing ruin; "the stock market crashed on Black Friday"; "a calamitous defeat"; "the battle was a disastrous end to a disastrous campaign"; "such doctrines, if true, would be absolutely fatal to my theory"- Charles Darwin; "it is fatal to enter any war without the will to win it"- Douglas MacArthur; "a fateful error"
Antonym: fortunate (indirect, via unfortunate)
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