Post-Office box vs POB

Post-Office box and POB both are nouns.

Word	Noun	Adjective	Verb	Adverb
Post-Office box	Yes	No	No	No
POB	Yes	No	No	No

As nouns, Post-Office box and POB are synonyms defined as:

Post-Office box and POB: a numbered compartment in a post office where mail is put to be called for

Other synonyms of Post-Office box include call box, letter box, PO Box.

Post-Office box (noun)	POB (noun)
a numbered compartment in a post office where mail is put to be called for	a numbered compartment in a post office where mail is put to be called for