1. showing a brooding resentment or silent resentment; moody and refusing to be sociable or cheerful
2. dark and threatening in appearance
Usage: often used to describe weather or landscapes

Examples

• The teenager gave his parents a sullen look when they told him he was grounded.
• She sat in sullen silence, refusing to speak to anyone at dinner.
• His sullen attitude made it difficult for others to approach him.
• The sullen gray clouds promised rain before evening.
• After losing the game, the team walked off the field with sullen expressions.
• The sullen sky matched her dark mood perfectly.
• He remained sullen and uncooperative throughout the entire meeting.