Definitions from Wiktionary (fourth rail)

▸ noun:  (rail transport) An extra rail in addition to the third rail (live rail) which is used for current return purposes, mainly by London Underground, because of problems caused by using the running rails for current return underground.



▸ Words similar to fourth rail
▸ Usage examples for fourth rail

▸ Idioms related to fourth rail
▸ Wikipedia articles (New!)
▸ Words that often appear near fourth rail
▸ Rhymes of fourth rail

▸ Invented words related to fourth rail