persona non grata. / Latin (pɜːˈsəʊnə nɒn ˈɡrɑːtə) / noun plural personae non gratae (pɜːˈsəʊniː nɒn ˈɡrɑːtiː) an unacceptable or unwelcome person. a diplomatic or consular officer who is not acceptable to the government or sovereign to whom he or she is accredited.