The words share the same Latin root meaning “cloudy,” but “nebulous” gained more of a foothold in the English language than “nubilous.” Both share similar definitions as well: They are adjectives for a cloudy or misty scene, but they also can be used figuratively for an unclear situation or sentiment. So, when should you use “nubilous” instead of “nebulous”? For a writer with a lyrical style, the choice is nubilous.