Causing or involving calamity; disastrous.(adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "calamitous" in a sentence
"By this it appears that it was advisable and seasonable only in calamitous times, and times of present distress, 1"
"To give to them who are thus marked an assurance of God's favour, that they may know it themselves; and the comfort of knowing it will be the most powerful support and cordial in calamitous times."
"Such an attack would truly be "calamitous" -- to use the same description as the Chairman of the U.S. Joint Chiefs of Staff, Admiral Michael Mullen."