An officer is an an individual with a position of authority or command in a rigidly hierarchical organisation, especially in the context of law enforcement or military forces. In most countries, it is used in the context of a "police officer", being a generic term for an officer of the law rather than signifying a particular rank.
In the wizarding world, the term was used in a similar manner. At the British Ministry of Magic, for example, it was used generically to refer to witches and wizards in their employ tasked in various ways with law enforcement. A celebrated Auror, Cerberus Langarm, as well as Myra Curio, of the Misuse of Muggle Artifacts Office, was known examples of "Magical Law Enforcement Officers" at the Ministry.
- Fantastic Beasts: Cases from the Wizarding World (First mentioned)