2. having momentous consequences; of decisive importance;
"that fateful meeting of the U.N. when...it declared war on North Korea"- Saturday Rev"the fatal day of the election finally arrived"
3. (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"