PO vs enlisted officer

PO and enlisted officer both are nouns.

Word	Noun	Adjective	Verb	Adverb
PO	Yes	No	No	No
enlisted officer	Yes	No	No	No

As nouns, enlisted officer is a hypernym of PO; that is, enlisted officer is a word with a broader meaning than PO:

PO: a noncommissioned officer in the Navy or Coast Guard with a rank comparable to sergeant in the Army
enlisted officer: a military officer appointed from enlisted personnel

Other hypernyms of PO include noncom, noncommissioned officer.

PO (noun)	enlisted officer (noun)
an independent agency of the federal government responsible for mail delivery (and sometimes telecommunications) between individuals and businesses in the United States	a military officer appointed from enlisted personnel
a noncommissioned officer in the Navy or Coast Guard with a rank comparable to sergeant in the Army