clam up
US /klæm ʌp/
UK /klæm ʌp/
1.
閉口不言, 守口如瓶
to suddenly stop talking, especially when you are expected to speak
:
•
When the police started asking questions, he just clammed up.
當警察開始提問時，他只是閉口不言。
•
She tends to clam up when she's nervous.
她緊張時往往會閉口不言。