clam up (to) [exp]

Meaning:

• to stop talking unexpectedly because you are nervous or shy.

Examples:

1. He was talking to me quickly. When the door was knocked, he clammed up.
2. An explosion was heard we all clammed up.
3. When asked about his role in the prank, Jake clammed up and refused to say another word.
4. She clammed up during the interview because she was nervous about saying the wrong thing.
5. The witness started to clam up when the lawyer pressed her for details about the incident.
6. Whenever the topic of his ex comes up, he completely clams up.
7. The suspect clammed up as soon as the police asked about his whereabouts on the night of the crime.