outerchange/ˌaʊ.tə(ɹ)ˈtʃeɪndʒ/EtymologyFrom outer + change by analogy with interchange.nounA connection between two stations within walking distance of each other but which are not physically connected; used especially where a journey involving such a connection can be done on a single ticket.“The five minute walk between Northwick Park and Kenton tube stations is a valid outerchange.”