From Longman Dictionary of Contemporary Englishbrownfield sitebrown‧field site /ˈbraʊnfiːld ˌsaɪt/ noun [countable] British English a place, especially in a city, that is used for building homes, offices etc, where in the past there have already been buildings, industries etc → greenfield siteFrom Longman Business Dictionarybrownfield siteˈbrownfield ˌsitePROPERTY a site used for building where there has already been building, industrial activity etc, especially in a town or cityThe government wants to raise the proportion of housing built on brownfield sites, rather than on unspoilt countryside. → site