n ( AmE )
a string of numbers following the name of a state at the end of a postal address in the US. ‘ZIP’ is an abbreviation for the Zone Improvement Plan, a system introduced by the US Postal Service in 1963. The word ‘zip’ also suggests speed, because the numbers help mail to be delivered quickly. ZIP codes have five numbers, and ZIP+4 Codes have five numbers and another four numbers separated by a hyphen, e.g. NY 10016-4314.
Compare postal district .