- outerchange
- noun /ˌaʊ.tə(ɹ)ˈtʃeɪndʒ/A 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 done on a single ticket.
The five minute walk between Northwick Park and Kenton tube stations is a valid outerchange.
Wikipedia foundation.