Which term means to pacify or calm someone down?

The term that means to pacify or calm someone down is "mollify." When you mollify someone, you are taking steps to soothe their feelings, lessen their anger, or bring about a sense of calm. This is often used in contexts where emotions are high and there is a need to ease tensions or alleviate distress.

In contrast, the other options do not convey the same meaning. "Rescind" refers to the act of formally withdrawing or canceling something, often used in legal contexts regarding agreements or decisions. "Sanction" can mean either to approve or to impose a penalty, which relates to regulation or discipline rather than calming emotions. "Rhetoric" involves the art of persuasive speaking or writing, focusing on how something is communicated rather than on soothing or calming someone. Thus, "mollify" is distinctly the best choice to capture the idea of pacifying or calming someone down.