That is the correct spelling of "ominous" (foreboding).
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The word "ominous" comes from the word "omen". An ominous dream
is one which contains signs of what is going to happen in the
future.
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No, "ominous" is already an adjective and does not have a direct verb form. You can use phrases like "seem ominous" or "carry an ominous tone" to express the concept in a sentence.