postcode UK /ˈpəʊs(t)kəʊd/US /ˈpoʊs(t)ˌkoʊd/noun 3verb 1forms 3 noun3 •(UK, Ireland) A sequence of letters and numbers added to a postal address to aid the sorting and delivery of post or mail. •(Australia, New-Zealand) A four-digit number added to a postal address to sort and deliver mail. •(UK, Ireland) The region denoted by such a sequence.The Environment Agency says it is mainly the most deprived postcodes that are the most flood-prone. — 2007 verb1 •(UK) To give a postcode to; to mark with a postcode. formspostcoded · postcoding · postcodes