gatefold
From Longman Business Dictionarygatefoldgate‧fold /ˈgeɪtfəʊld-foʊld/ adjective [only before a noun] a gatefold page in a book or magazine is bigger than the other pages, with the edges folded to the middle so that it can be opened out. Gatefold pages are used for large pictures, photographs etcThe campaign will featuregatefold ads in all of trade magazines.