1) Military rank of Canada 2) Naval rank 3) Navy noncom 
A petty officer is a non-commissioned officer in many navies and is given the NATO rank denotion OR-6. They are equal in rank to sergeant in the British Army and Royal Air Force. A petty officer is superior in rank to leading rate and subordinate to chief petty officer, in the case of the British armed forces. ==Origins== The modern petty officer ...
[n] - a noncommissioned officer in the navy with a rank comparable to sergeant in the army
PO noun a noncommissioned officer in the navy with a rank comparable to sergeant in the army