ما هو تعريف "الكي" في الشرع وما المقصود منه؟

Cauterization is the burning of the skin. It has been forbidden in several hadiths, and the prohibition was said to be either because people glorified it and believed it would cure diseases, or if it was used preemptively before there was a need for it, or as a matter of reliance [on Allah]. There is no punishment by cauterization in Islamic law; rather, torture by fire is forbidden, because torturing with fire belongs exclusively to Allah.