PO box
noun [ C ] uk/ˈpiː.əʊ ˌbɒks/ us/ˈpiː.oʊ ˌbɑːks/
邮政信箱
a box with a number in a post office to which your letters and parcels can be sent and from which you can collect them
Write to PO box 123. 来信请寄123号邮政信箱。
a PO box number 邮政信箱号