RAIL (4 letters) The term SOME RAILS can be broken down into two words, ELS and RAIL. ELS is an abbreviation for the term 'electronic switching system' which is a type of computerized telephone exchange used in telecommunications. RAIL is an acronym for 'regional advanced interconnect link' which is a type of high-speed data communication network. Together, these two terms refer to a system of electronic switching systems and regional advanced interconnect links that are used to facilitate communication between different networks.