clam up
US /klæm ʌp/
UK /klæm ʌp/
1.
闭口不言, 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.
当警察开始提问时，他只是闭口不言。
•
She tends to clam up when she's nervous.
她紧张时往往会闭口不言。