What is another word for button lip?
Pronunciation: [bˈʌtən lˈɪp] (IPA) 
The phrase "button lip" refers to a person who remains quiet, tight-lipped, and doesn't speak or share information. Other common synonyms for this phrase include "keep quiet," "hold your tongue," "don't say a word," "stay mum," "keep mum," "be silent," "shut up," "zip it," "seal your lips," and "clam up." These phrases are often used in situations where it's best to remain silent to avoid any misunderstandings or negative consequences. However, it's also important to note that there are situations where it's appropriate to speak up and communicate one's thoughts and feelings.
