keep a straight face
US /kiːp ə streɪt feɪs/
UK /kiːp ə streɪt feɪs/

1.
정색하다, 웃지 않다
to succeed in not laughing or smiling
:
•
It was hard to keep a straight face when he told that ridiculous joke.
그가 그 우스꽝스러운 농담을 했을 때 정색하기 어려웠다.
•
She tried to keep a straight face, but a giggle escaped.
그녀는 정색하려고 노력했지만, 웃음이 터져 나왔다.