noun (n)

• a commissioned military officer(noun.person)

  source: wordnet30
• an officer in a police force(noun.person)

  Synonym:
  police lieutenant
  

  source: wordnet30
• an assistant with power to act when his superior is absent(noun.person)

  Synonym:
  deputy
  

  source: wordnet30
• an officer holding a commissioned rank in the United States Navy or the United States Coast Guard; below lieutenant commander and above lieutenant junior grade(noun.person)

  source: wordnet30
• An officer who supplies the place of a superior in his absence; a representative of, or substitute for, another in the performance of any duty.(noun)

  source: webster1913