postcodepost·code /ˈpəʊstkəʊdˈpoʊstkoʊd/ (also postal code) noun [countableC] British EnglishBrE a series of letters and numbers showing exactly where a building is. Postcodes are used so that post can be delivered more quickly. Insurance companies also use postcodes to calculate insurance rates in different areasSYN AmE zip codeA specialist agency will add postcodes to addresses where customer records are incomplete.