1. having momentous consequences; of decisive importance

- that fateful meeting of the U.N. when...it declared war on North Korea

- the fatal day of the election finally arrived

Similar word(s): decisive, fatal

2. ominously prophetic

Similar word(s): prophetic, prophetical, foreboding, portentous

3. (of events) having extremely unfortunate or dire consequences; bringing ruin

- 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

Similar word(s): unfortunate, black, calamitous, disastrous, fatal

4. controlled or decreed by fate; predetermined

- a fatal series of events

Similar word(s): inevitable, fatal

Sentences with fateful as an adjective:

- It started with that fateful trip, history was never the same afterwards.