WordNet sense 1 (a member of a police force):

policeman, police officer

WordNet sense 2 (a person authorized to serve in a position of authority on a vessel):

ship's officer

WordNet sense 3 (someone who is appointed or elected to an office and who holds a position of trust):

officeholder

WordNet sense 4 (any person in the armed services who holds a position of authority or command):

military officer