bad-tempered and sulky; gloomy
This vocabulary word was written in “The Shawl” by Louis Erdrich.
Her name was Aanakwad, which means cloud, and like a cloud she was changeable. She was moody and sullen one moment, her lower lip jutting and her eyes flashing, filled with storms.
This sentence is describing how Aanakwad felt and what type of person she is. The narrator was introducing this character to us as readers. One of word was sullen which I learned it means to be upsetting and ill humor, they may keep to themselves and have dark gray days.
Source: Google search engine “sullen”