What is clam up

clam up

vb. (context intransitive idiomatic English) To become silent; to stop talking, to shut up.

clam up

v. refuse to talk or stop talking; fall silent; "The children shut up when their father approached" [syn: close up, dummy up, shut up, belt up, button up, be quiet, keep mum] [ant: open up]

If Watson started teasing him in front of the others about his daughter's wild ideas, he'd clam up completely.

I was having a hard time keeping the judgment out of my voice, afraid if she sensed the full range of my outrage, she'd clam up.

They don't want any dirty laundry flapping around in the breeze, so they clam up.

If she catches on, she might clam up, and that'd make things difficult.

If he pressed her about the situation, she might very well clam up and refuse to tell him anything.

When I explained about him, it made her clam up, and she cut the tour short.

What is "clam up"