فَهُوَ طَلَبُ الْكَفِّ عَنِ الْفِعْلِ عَلَى وَجْهِ الِاسْتِعْلَاءِ
Prohibition is a request to refrain from an action, expressed in a manner of authority.
Ṭalab al-kaff asks someone not to undertake or to discontinue an action. ʿAn al-fiʿl identifies the action from which the person is to refrain. ʿAlā wajh al-istiʿlāʾ describes the authoritative manner of the request.
The definition concerns the primary, literal force of prohibition. When the same form serves another purpose, context and communicative cues determine its meaning; it need not always be an authoritative ban.