What is another word for clam up?
Pronunciation: [klˈam ˈʌp] (IPA) 
Clam up is a phrase that means to become silent or refuse to talk about something. However, there are many synonyms for this phrase, such as hush, shut up, be quiet, keep mum, and seal one's lips. Other synonyms for clam up include staying tight-lipped, becoming mute, remaining silent, buttoning your lip, or zipping your mouth. In certain contexts, the phrase may also be substituted with terms such as going silent, losing one's voice, or withdrawing from conversation. Regardless of the synonym used, the underlying meaning remains the same, as it describes a situation where someone becomes unwilling or unable to speak their mind.
