1) Appalling 2) Black 3) Bringing ruin 4) Calamitous 5) Cataclysmic 6) Damaging 7) Fatal 8) Fateful 9) Foreboding disaster 10) French word used in English 11) Harmful 12) Ruinous 13) Shattering 14) Terrible 15) Tragic 16) Unfortunate 17) Very unfortunate Found on https://www.crosswordclues.com/clue/disastrous
• (a.) Attended with suffering or disaster; very unfortunate; calamitous; ill-fated; as, a disastrous day; a disastrous termination of an undertaking. • (a.) Full of unpropitious stellar influences; unpropitious; ill-boding. Found on http://thinkexist.com/dictionary/meaning/disastrous/
[Adjective] Something that fails to do well or goes badly wrong. Example: The play had disastrous reviews and closed after two days.
Found on http://www.bbc.co.uk/skillswise/glossary/
Dis·as'trous adjective [ Confer French désastreux . See Disaster .] 1. Full of unpropitious stellar influences; unpropitious; ill- boding. [ Obsolete] « The moon In dim eclipse, disastrous twilight sheds.» Milton. 2. Attended with suffering ... Found on http://www.encyclo.co.uk/webster/D/75
causing great distress or injury; ruinous; very unfortunate; calamitous: The rain and cold proved disastrous to his health. · foreboding disaster. Found on https://www.infoplease.com/dictionary/disastrous