na-adjective, noun
bad mood; displeasure; sullenness
Describes a visibly unhappy, sulky, or irritable state. Often used with ～な, ～になる, or ～そう. The antonym is 上機嫌 (good mood).
See also: 上機嫌
彼は朝から不機嫌だ。
He has been in a bad mood since morning.
不機嫌
Please don't make such a sullen face.