noun
one's mood; one's caprice; a smile or a frown
yojijukugo (four-character idiom)
社長の**一顰一笑**に、部下たちはいつも気を遣っている。
- The subordinates are always walking on eggshells around the president's every facial expression, whether he is smiling or frowning.
彼の**一顰一笑**次第でプロジェクトの成否が決まるのは、さすがにプレッシャーだ。
- It's quite a lot of pressure, knowing that the success or failure of the project depends entirely on his every mood and expression.