Noun
master chief petty officer (plural master chief petty officers)
(US, Navy) A non-commissioned officer in the United States Navy and United States Coast Guard, ranking above senior chief petty officer.
Formerly Chief Master Sergeant and Master Chief Petty Officer were the highest enlisted ranks and rates, the former being the highest rank of precedence for Army, Air Force and Marine NCOs. Source: Internet
Today only the rank of First Master Chief Petty Officer is unused yet but the rank of First Chief Master Sergeant is now being applied. Source: Internet
Team Navy member Master Chief Petty Officer Raina Hockenberry celebrates after winning the 50-meter freestyle swim category during the DoD Warrior Games, June 8, 2018. Source: Internet