Which term describes a substance used to smooth or polish?

The term that describes a substance used to smooth or polish is abrasive. Abrasives are materials that are commonly used in various applications to grind, cut, or wear away material to create a smooth surface. They can be found in products such as sandpaper, polishing compounds, and grinding wheels, which are designed to refine surfaces by removing roughness or imperfections. In contrast, chagrin refers to a feeling of embarrassment or annoyance, complacent means showing a smug or uncritical satisfaction with oneself, and defamation involves the act of damaging someone's good reputation by making false statements. These other terms do not pertain to the action of smoothing or polishing, highlighting the specific and appropriate nature of "abrasive" as the correct choice.