The phrase "shutting mouth" is commonly used to describe someone who is keeping quiet or maintaining silence. However, there are many synonyms for this phrase that can be used interchangeably in different contexts. Some examples include "keeping mum," "sealing lips," "zipping mouth," "closing off," and "clamping down." Each of these phrases provides a slightly different connotation, from choosing to remain silent to actively suppressing speech. Other synonyms include "hushing up," "muzzling," "quenching," and "stifling." Depending on the situation, any of these phrases can be used to convey the idea of someone intentionally refraining from speaking or revealing information.