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fourth rail

noun

Definitions

  1. An extra rail in addition to the third rail (live rail) which is used for current return…

    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.

    • The railway used the 'Third Rail' system of electrification, like all the early Tubes. (But it would soon be replaced across the network by another system even more exciting - Fourth''' Rail!)

The neighborhood

Vish — recursive loop

No curated loop yet for fourth rail. Loops are being traced one word at a time while the ingestion pipeline matures.

sense glosses and etymology drawn from English Wiktionary · source · CC-BY-SA