1. (noun)military officer, officer any person in the armed services who holds a position of authority or command
"an officer is responsible for the lives of his men"
2. (noun)officeholder, officer someone who is appointed or elected to an office and who holds a position of trust
"he is an officer of the court"; "the club elected its officers for the coming year"
3. (noun)policeman, police officer, officer a member of a police force
"it was an accident, officer"
4. (noun)officer, ship's officer a person authorized to serve in a position of authority on a vessel
"he is the officer in charge of the ship's engines"