封口 (fēng kǒu) literally means 'seal mouth'—'封' means 'to seal, close, or block', and '口' means 'mouth'. Together, it metaphorically refers to suppressing speech or preventing someone from speaking out, especially about sensitive or confidential information. It commonly appears in legal, medical, or corporate contexts where confidentiality is enforced.

In practice, 封口 often implies coercion or pressure—not just voluntary silence—but can also describe formal measures like non-disclosure agreements or court-ordered gag orders. While it may sound physical (like literally gagging someone), it’s almost always figurative. It carries a slightly negative or suspicious connotation, suggesting secrecy, cover-up, or abuse of power rather than neutral confidentiality.