Wiktionary
n. A sequence of letters and/or numbers added to a postal address to aid the sorting and delivery of post / mail.
WordNet
Wikipedia
A postal code (also known locally in various English-speaking countries throughout the world as a postcode, post code, Eircode, PIN Code or ZIP Code ) is a series of letters and/or digits, sometimes including spaces or punctuation, included in a postal address for the purpose of sorting mail.
In February 2005, 117 of the 190 member countries of the Universal Postal Union had postal code systems.
Although postal codes are usually assigned to geographical areas, special codes are sometimes assigned to individual addresses or to institutions that receive large volumes of mail, such as government agencies and large commercial companies. One example is the French CEDEX system.
Usage examples of "postal code".
There was nothing on the outside but my house number and postal code, no return address, only a handwritten routing number in the left corner.
I swear to God, your own mother used to say you had the weakest mind in your entire postal code.
Or order your copy now by sending your name, address, zip or postal code, along with a check or money order (please do not send cash) for $5.
I think I may have got stuck for a moment on the middle name of my geography teacher, and I definitely hesitated on the postal code of the midwife who attended the birth of my great-grandmother, but otherwise I sailed through it without a hitch.