indication, sign, portent, forerunner
Conjecture, omen, prophecy, augury...
omen
alerts, warns, admonition, counsels, forewarning, hints, omen, sign, tip-off
The word omen is not a bad word
Thesauruses and dictionaries do not seem to mention what the antonym of an omen is, but they do mention that and omen is a "sign of something to come." So, if an omen means to predict something that has not happened yet, then the opposite of an omen would either be to predict what has happened long ago or something that has already happened.
Omen
The word omen is an abstract noun.
That was not a good omen.
Omen = 'ōuli
omen,portent, augury, sign, indication, token, prediction
omen means in portuguese: presságio, agouro
EX.. my dogs is a omen dogs