WordNet (r) 3.0 (2006):

persona non grata
    n 1: a diplomat who is unacceptable to the government to which
         he is sent
    2: a person who for some reason is not wanted or welcome [syn:
       unwelcome person, persona non grata]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "persona non grata":
   DP, Ishmael, Jim Crow, alien, apartheid, bad child, bad example,
   bad man, bad news, bad person, bad woman, castaway, color bar,
   declasse, derelict, displaced person, disreputable,
   disreputable person, division, ethnocentrism, evictee,
   exclusiveness, exile, expatriate, expellee, foreigner, insularity,
   insulation, isolation, know-nothingism, leper, narrowness,
   objectionable person, out-group, outcast, outcast of society,
   outcaste, outlaw, outsider, pariah, parochialism, quarantine,
   race hatred, racial segregation, seclusion, segregation,
   separation, snobbishness, social outcast, stranger, tightness,
   unacceptable person, undesirable, untouchable, unworthy,
   xenophobia