A bad-tempered or gloomy person is sullen. Sullen people are down in the dumps.

If someone is dark, dour, glum, moody, morose, or sour, they're also sullen. Teenagers are often described as sullen, especially when they're being grumpy and silent. You often hear about "a sullen silence," which is when someone is quiet, but obviously in a lousy mood. If a sullen person is talking, they're probably not saying much, and they might not be doing much beyond grunting. A sullen person isn't much fun to be around.

Definitions of sullen

adj showing a brooding ill humor

“a sullen crowd”
dark, dour, glowering, glum, moody, morose, saturnine, sour
having an irritable and unpleasant disposition

adj darkened by clouds

heavy, lowering, threatening
full of or covered with clouds

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