Noun
petty officer third class (plural petty officers third class)
(US, Navy) A non-commissioned officer in the United States Navy and United States Coast Guard, ranking above seaman and below petty officer second class.
Petty Officer Third Class Maxim Cravet, Health Promotions Hospital Corpsman at Navy Medical Readiness and Training Command Pearl Harbor (NMRTC PH), developed a workout program with space and movement restrictions in mind. Source: Internet