المَحْكُومُ عَلَيْهِ هُوَ الشَّخْصُ الَّذِي يَتَعَلَّقُ بِفِعْلِهِ خِطَابُ الشَّارِعِ، وَقَدْ سَمَّى العُلَمَاءُ هَذَا الشَّخْصَ المُكَلَّفَ. [تَيْسِيرُ التَّحْرِيرِ، ج ٢، ص ٣٩٥]

Al-Mahkoom ‘Alaihi is the person upon whom the address of the legislator is attached to his action and the ‘Ulamaa have called this person the Mukallaf (Ref: Tayseer At-Tahreer Vol. 2 P. 395).