(adj) having momentous consequences; of decisive importance; - Saturday Rev, Syn. fatal, Example:that fateful meeting of the U.N. when...it declared war on North Korea; the fatal day of the election finally arrived
(adj) (of events) having extremely unfortunate or dire consequences; bringing ruin; ; ; ; - Charles Darwin; - Douglas MacArthur, Syn. disastrous, calamitous, fateful, fatal, Example: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; it is fatal to enter any war without the will to win it; a fateful error