clam up

Definition

To become silent; to stop talking.

Etymology

By analogy with a clam closing itself. Compare clamshell (“mouth”), clam (“mouth”).

Example Sentences

• "Maybe he … or she … was a witness who refused to clam up … a whistle blower …"
• "Teenagers' father. Alright, Matt, I think you've made your point. Matt Foley: Dad, I sincerely wish you'd do everyone a great service, and clam up!"