keep a straight face

US /kiːp ə streɪt feɪs/
UK /kiːp ə streɪt feɪs/
"keep a straight face" picture
1.

garder son sérieux, ne pas rire

to succeed in not laughing or smiling

:
It was hard to keep a straight face when he told that ridiculous joke.
C'était difficile de garder son sérieux quand il a raconté cette blague ridicule.
She tried to keep a straight face, but a giggle escaped.
Elle a essayé de garder son sérieux, mais un petit rire lui a échappé.