In a sullen, taciturn, or morose manner; keeping silent and showing displeasure or sulkiness.
彼はむっつりと座っていて、ほとんど何も話さなかった。
He sat sullenly and hardly said anything.
朝からむっつりしている理由を聞いたら、仕事で失敗したと言った。
When I asked why he had been so morose since morning, he said he messed up at work.
むっつりしていると距離を感じられるから、笑顔で話しかけた。
Because his sulky silence made me feel distant, I greeted him with a smile.
A taciturn or uncommunicative person; someone who is sulky and not talkative.
彼はむっつりで、初対面の人とはあまり話さない。
He's taciturn and doesn't talk much with people he meets for the first time.
田中さんはむっつりだから、冗談も通じにくいことがある。
Tanaka is a quiet person, so sometimes jokes don't get through to him.