How would you describe someone who is sulky and gloomy?

Describing someone as sulky and gloomy indicates a manner that is typically characterized by a brooding or silent resentment, often accompanied by a lack of enthusiasm or cheerfulness. The term that best fits this description is "sullen." A sullen person often appears moody and withdrawn, reflecting a feeling of sadness or displeasure without engaging positively with those around them.

On the other hand, the other words have distinct meanings that do not align with the characteristics of being sulky and gloomy. "Supercilious" refers to an attitude of arrogance or disdain, suggesting a sense of superiority over others. "Tacite" appears to be a misspelling; the intended word could be "tacit," which relates to something understood or implied without being stated, and does not convey mood. "Transient" describes something temporary or short-lived, which does not relate to the emotional state of a person. Thus, the term "sullen" is indeed the correct choice for describing someone who exhibits a sulky and gloomy demeanor.