What is the ruling on saying "You are a μa’raṣ" and what does it mean?

This term is one of the euphemisms for slander (qadhf). The ruling on insulting with it varies according to custom (ʿurf), common usage (ishtihār), and prevailing circumstances (qarāʾin al-ḥāliyyah). Ibn Nujaym mentioned that one who uses the term "muʿarris" should be subjected to taʿzīr (discretionary punishment) because it refers to a "dayyūth" (pimp or cuckold) in the custom of Egypt and Syria. Al-Buhūtī stated that whoever says, "Yā muʿarris" or "Yā ʿarsa," should be subjected to taʿzīr. These terms should be considered explicit (ṣarīḥayn) according to custom. Similar to them is "Yā dayyūth," which refers to one who condones evil upon his family.