noun (n)

• a disloyal person who betrays or deserts his cause or religion or political party or friend etc.(noun.person)

  Synonym:
  apostate, deserter, recreant, renegade, turncoat
  

  source: wordnet30
• any of several breeds of terrier developed to catch rats(noun.animal)

  Synonym:
  rat terrier
  

  source: wordnet30
• One who, or that which, rats, as one who deserts his party.(noun)

  source: webster1913