clam up

verb

1. informal,  (intr, adverb) to keep or become silent or withhold information

Idioms and Phrases

Refuse to talk or respond, as in Whenever she asks her teenager about his activities, he clams up. This term alludes to the tightly closed valves of a live clam. [Slang; early 1900s]

Related Words

• allay 
• appease 
• assuage 
• hush 
• mollify 
• muffle 
• muzzle 
• pacify 
• please 
• relax 
• satisfy 
• soften 
• soothe 
• squelch 
• subdue