Omen n. : An occurrence supposed to portend, or show the character of, some future event; any indication or action regarded as a foreshowing; a foreboding; a presage; an augury.

Omen v. t. : To divine or to foreshow by signs or portents; to have omens or premonitions regarding; to predict; to augur; as, to omen ill of an enterprise.

Example:
What was seen as a bad Omen at the begging of the opera "Prince Igor"?

Taxonomy
omen, election, bad omens, journey, bad omen, good omen, medicine, free encyclopedia, portents, treatises, pot, fruit, clothes, tree, wearing white, Astrology, Divination, appearance.

Defination from the web:
omen (also called portent or presage) is a phenomenon that is believed to foretell the future, often signifying the advent of change. ... Ancient Roman religion employed two distinct types of professional omen readers. ...