Used mimetically to indicate being offended, annoyed, or sulky; often used as ムッとする or ムッとした.
彼の一言に彼女はムッとした。
She bristled at his remark.
上司の注意で彼はムッとした顔をした。
He made an annoyed face when his boss scolded him.
冗談がきつすぎて皆がムッとしている。
The joke was too harsh and everyone is offended.
Onomatopoeic for a stuffy, muggy, or oppressive feeling in the air (stifling).
梅雨のせいで部屋の中がムッとする。
Because of the rainy season, the room feels muggy.
汗をかくと首の後ろがムッとする感じがする。
When I sweat, the back of my neck feels stuffy.
Can describe shutting one's mouth tightly or clamping one's lips shut (firmly).
彼は何も言わずに口をムッと結んだ。
He said nothing and pressed his lips together.
批判を受けて彼女はムッと口を閉ざした。
After being criticized, she clamped her mouth shut.