What is the meaning of Chief_petty_officer?

A warrant officer belonging to one of the two classes of chief petty officer: chief petty officer first class and chief petty officer second class.

A non-commissioned officer in the Royal Navy, ranking above petty officer and below warrant officer class 2.

A non-commissioned officer in the United States Navy and United States Coast Guard, ranking above petty officer first class and below senior chief petty officer.

Source: wiktionary.org