a system used in the U.S. to facilitate the delivery of mail, consisting of a five- or nine-digit code printed directly after the address, the first five digits (initial code) indicating the state and post office or postal zone, the last four (expanded code) the box section or number, portion of a rural route, building, or other specific delivery location.
Also, ZIP code, Zip code .
[ 1960-65, Amer.; Z ( one ) I ( mprovement ) P ( rogram ) ]