Wiktionary
n. (context US Navy English) A non-commissioned officer in the United States Navy and United States Coast Guard, ranking above seaman and below petty officer second class.
Wikipedia
Petty officer third class is the fourth enlisted rank in the U.S. Navy, U.S. Coast Guard, and the United States Naval Sea Cadet Corps, just above seaman and below petty officer second class, and is the lowest rank of non-commissioned officer, equivalent to a corporal in the U.S. Army and Marine Corps. Petty officer third class shares the same pay grade as senior airman in the Air Force, which no longer has an NCO rank corresponding with E-4.
Usage examples of "petty officer third class".
The quartermaster, Petty Officer Third Class Pollard, was standing right next to me, and he was hit.
He glanced at the navy rating who, under the supervision of a petty officer third class, had begun setting up a holoprojector next to the lectern while Conorado spoke.
Daly identified himself to the petty officer third class standing guard outside the open hatch of Captain Emmerts stateroom.
Aboard Angela Martens, it was Petty Officer Third Class Cassius Bradford, a much put upon individual, who, in his own unbiased opinion, should have been at least a chief petty officer by now.